In a Finder window using Icon view, including the Desktop, if the icon size is set to 64x64 or greater, .pdf, .key, and .ppt files will have forward and backward arrows overlaid when you mouse over their icons. Clicking these arrows allows you to page through the document one page at a time.
Previewing the document with Quick Look, viewing a different page, and then closing Quick Look changes the icon view preview to the new page. You can then continue to page through the document with the overlaid forward and backward buttons from the new location.
One caveat: previewing with Quick Look only updates the icon to the new page if you used the overlaid forward or backward buttons on the icon at least once before opening Quick Look.
Taking focus off the icon returns the icon preview to the first page of the document.
For a year or more, I've been having trouble with application icons frequently not copying when I copy a file from one folder to another in the Finder. I would get a generic icon on the copied file, and have to copy and paste the icon from the original to the copy. The problem persisted after I upgraded to Snow Leopard. I concluded that it was an incurable Finder bug -- no amount of system maintenance would fix it.
Then I found a little free app, Refresh Finder, that solved the problem (there are a few other apps that do the same thing). Rather than restarting the Finder, these apps just refresh the window, and the icons appear as they should on recently-copied files.
As it happens, this window refresh issue has been around for a long time; other manifestations include files moved or copied or downloaded to a folder not showing up. I guess I was just being dense, but I didn't connect the two (mis)behaviors. But they are, it seems, one and the same problem. Anyway, you can drag and drop the Refresh Finder app to the Finder's tool bar to have it handy in every window; just click on it whenever either of these window refresh problems occurs. For me, it is a simple and welcome solution to a vexing problem.
[robg adds: Macworld's Dan Frakes covered Refresh Finder as a Macworld Gems entry a couple years back. As Dan explains in his article, Refresh Finder is a front end to a relatively simple AppleScript:
tell application "Finder"
tell front window
update every item with necessity
If you're running Snow Leopard, create a new Service in Automator, set it to work in Finder (receives no input), and then add the Run AppleScript action to your Service. Save your Service, and you can then (using the Keyboard Shortcuts tab of the Keyboard System Preferences panel) assign it a keyboard shortcut. Now you can refresh a Finder window via the keyboard.]
Snow Leopard adds the ability to play audio files directly from a Finder window in Icon view (including your Desktop); 10.5 can play audio files in the Preview column when in Column view mode. Hover your cursor over the icon in Icon view, and a play/pause button will appear. As long as you do not change the selection in the Finder, the audio will continue to play even if you switch applications.
In Icon View, this integrates cleanly with Quick Look. You can press the Space Bar to open Quick Look on a playing audio file, and Quick Look will take over with no skips or jumps in the sound. Switching applications with Quick Look open still halts the audio, but another press of the Space Bar to hide Quick Look before going back to work will let you keep working to the music.
Unfortunately, Quick Look does not work as smoothly in Column View. Both the Preview column's player and Quick Look track their place in the file separately. Quick Look pauses the Preview column's player when it is opened and starts the audio from the beginning, but does not unpause in the same way when it is closed.
[robg adds: In 10.5, when previewing audio in column view, opening a Quick Look window would actually play the audio file twice, with no sync at all between the two.]
Quick Look has a hidden feature that is not enabled by default, and can only be enabled through Terminal. Essentially, when 'X-Ray mode' is turned on, Quick Looking a folder will show, in a way, the contents of the folder.
Instead of just seeing the regular folder icon in Quick Look, the folder icon will be semi-transparent, with previews of the folder's contents visible in the Quick Look window, as seen in the image at right. What's more, the preview images will rotate automatically, moving through each item in the folder (click the image to see a movie of the animation).
To turn this on, quit the Finder (using Activity Monitor, Terminal, etc.), then open Terminal and enter this command:
Relaunch the Finder, and enjoy the new folder X-Ray mode in Quick Look. If you ever want to disable it again, quit the Finder, then repeat the above Terminal command, but change the 1 to a 0.
[robg adds: The image and movie above are from my machine; I added them to make it more clear exactly how this feature works. While it's a nice visual effect, I'm not sure how really useful it may be. Update: Hint republished to note that it works in both 10.5 and 10.6.]
When navigating the Finder in column view in 10.6, the system now allows the use of Tab/Shift-Tab to go forwards and backwards in the folder hierarchy. Unlike (for me at least) 10.5, the arrow keys also work reliably for that now.
Another interesting tweak is that using Tab/Shift-Tab does not change the current working directory, so you can hit, for example, Shift-Tab three times, then hit Right Arrow once, and you'll be one folder deeper than you were when you started.
Here's an AppleScript that toggles the presence of the sidebar in all Finder windows. Toggle status is determined by that of the front window. In Tiger, it sets the sidebar to its minimum width; in Snow Leopard, it hides it completely. The script leaves the toolbar alone.
After hastily upgrading to Snow Leopard, I found myself without various tools I had grown used to. One such tool was the SCPlugin, which provided a contextual menu for many operations with Subversion repositories.
After reading that Finder contextual plugins are now no longer possible (in the Ars Technica Snow Leopard review), I gave up hope of an update being released. Services are seemingly the nearest equivalent. Fortunately, Automator now makes making your own services relatively easy. I confess to never having used Automator before today, so this may not be the best way, but it at least goes some way to restoring the functionality I lost.
These two workflows provide Update and Commit commands, which is all I find myself in desperate need of right now. To create both, launch Automator and select Service from the initial screen.
In OS 10.0-10.2, there was no sidebar in Finder windows and commonly-used locations were chosen by clicking on an icon in the toolbar. When Apple added the sidebar in 10.3, they changed the functionality of both the sidebar and the toolbar so that it 'roots' you to whatever location you picked while in column view, i.e. removes the horizontal scroll bar so that you can't access lower-level directories.
There were only two ways around this: double-clicking command-up arrow, or using this hint. In Snow Leopard, the functionality of column view has changed again. Now, when you have the sidebar visible, it still roots you to that spot. However, if you have the sidebar disabled (View » Hide Sidebar), clicking on an icon in the toolbar still gives you access to the entire file hierarchy with a horizontal scroll bar!
It's great; Apple finally let us reclaim all that unused space in the toolbar and gave us the ability to get rid of the sidebar by default (which is not an efficient use of space). It's a little buggy though, in that if you are previously rooted, you stay that way until you click on a lower level directory.
Incidentally, I'm typing this on the 13" MacBook Air, having previously had a 15" MacBook Pro and let me tell you, having the extra screen real estate without that sidebar there is great.
After several failed attempts to connect to iDisk in 10.6 (e.g. poor internet connection), Finder tends to crash with the error:
The application "Finder" cannot be opened
Finder then will not automatically restart. But there is a fix if you have Spotlight, Quicksilver, Google Quicksearch box, or some other access to Terminal. If you do, launch Terminal and type killall Finder, then press Return. Finder, although apparently not an active process (per the above error), will then restart immediately and successfully.
The following is more of an undocumented change than a hint.
In Finder's Column View (where I spend the vast majority of my time), if you use Select All (Command-A) with a folder is selected, previous releases of OS X would highlight the entire contents of the selected folder. In 10.6, I am seeing the behavior change to selecting the entire contents of the folder in which the selected folder resides.
This actually makes more sense because it is consistent with Select All used on a non-folder item, but it's going to take me a few days to re-calibrate my brain and fingers.
[robg adds: In testing this, I noticed that the behavior differs depending on how the folder is selected. If you select a folder with the mouse and then press Command-A, the behavior is the same as previous versions of OS X. But when you use the keyboard to select a folder, pressing Command-A highlights everything at the same level as the selected folder. I'm would think one behavior or the other is a bug; it seems they should be consistent.]