I think this is only possible in 10.5, but you can now organize Automator workflows in the Finder's contextual menu. Go to ~Library » Workflows » Applications » Finder, create folders, then drag and drop your workflows into them to organize them.
This is very handy if you have a lot of workflows there (which I do).
Viewing images in Cover Flow sometimes shows a high resolution preview, and sometimes not. At first I thought the Finder just needed time to "catch up," but I sat and waited a long time for a high res preview to be generated, and nothing ever happened.
It turns out Cover Flow will generate a high res preview only if a preview is not already associated with an image file. The existence of a preview depends on what application created the file. Photoshop creates a low res preview (by default, this can be changed in its prefs). So did Image Capture in Tiger. If you do a Get Info on one of these image files and delete the icon in the upper left, a new one will be instantly generated (even if Show Icon Preview isn't checked in View Options). Now, Cover Flow will show a high res preview.
[robg adds: Queue user fds points out that you can remove the icon from a number of files at once. Just select them all in the Finder then press Control-Command-I. Select the icon and delete, and you'll remove them all.]
This is not really a hint, but I think it's worth mentioning. The Finder preferences in 10.5 (Finder » Preferences) allow you to turn off the annoying dialog box that normally pops up when you change the extension of a filename. You'll find the setting on the Advanced tab.
[robg adds: The other new addition there is a checkbox to always securely empty the trash.]
I will often throw a bunch of files (web pictures, mostly) into a 'to be filed' folder for later renaming. The problem, however, is that when I rename a file, the Finder re-sorts the list, moving the renamed file. This forces me to scroll the window to find the next file to be renamed -- as it's now somewhere else in the window.
After all these years, I realized that if I first sort by file size in the Finder, the file list stays put and doesn't jump around so much, making the renaming task much easier.
[robg adds: As of 10.5, you can now sort a column view window, so this trick can work in those windows, too. I'll admit I'd never thought of this simple solution, despite running into the "jumping files" problem on a regular basis.]
New in 10.5 is the ability to add a keyboard shortcut for the Show Package Contents contextual menu item in the Finder. Simply open the Keyboard & Mouse System Preferences panel, select the Keyboard Shortcuts tab, click the "+" button, choose Finder as the Application, and type Show Package Contents as the command name. Set whatever shortcut keys you want to use, such as Command-Control-S, then click Add. That's it; you've now created a contextual menu shortcut for Show Package Contents.
In 10.4, the only way to add a keyboard shortcut to Show Package Contents in the Finder was with a combination of apple script and automator as detailed in this hint.
[robg adds: With the ability to set these keys on the fly now, you don't even have to restart the Finder. I tried creating shortcuts for the entries in the More sub-menu, but sadly, that didn't work (so no keyboard shortcuts for Automator workflows via the Finder).]
If you have a bunch of folders open in the Finder and you need to drag an icon to one of those folders, the folder you want to drag to may be behind another window. Therefore, you would have to bring it to the front first or use Exposť, but, this hint isn't about Exposť. Let me explain how to do this.
If you click and start dragging the file and then press Command-~, the Finder will not rotate through windows. Instead, try this. Click and hold on the file you want to drag but do not start dragging. Now press Command-~ to rotate through the open windows, stopping when the window you want is frontmost. Now start dragging your icon, and drop it wherever you like in the chosen window.
Also, if you are dragging a Application from a downloaded disk image, you can click and hold on the icon and press Command-Shift-A (or any of the other shortcuts in the Go menu), and the Applications window will pop to the front -- then you can continue to drag your file into it.
Well, the title says it all. For example, if you select items 01.jpg, 02.jpg, 03.jpg in the Finder and then copy, the order on the clipboard will be 01.jpg, 02.jpg, 03.jpg. However, if you select 03.jpg, 01.jpg, 02.jpg and copy, you'll have them in that order on the clipboard. You can sort it anyway you want ... 1, 3, 5, 2, 4, 6, etc.
This is extremely useful for me. No more rearranging attachments' order in Mail.app, for example.
[robg adds: In prior OS X releases, this is how it worked in column view mode, but not the other view modes. In 10.5, it seems to work in all view modes, based on my limited testing this morning.]
You may have noticed that .eps files do not work in Leopard's Quick Look -- only the icon with some file attributes is shown.
If you want to get a thumbnail icon and a preview in Quick Look, you may want to download the free EPSQuickLookPlugin and install it into your ~/Library/QuickLook folder (if there's no such folder, just create it). A restart may be necessary.
I had a look through the system library in the Finder's Cover Flow mode and discovered that quite a lot of icons still are in the old 128px size ... but what surprised me was the fact that Quartz Composer files automatically started to play. To have a look at these, just navigate to the main screen saver folder (/System » Library » Screen Savers). There you will have Arabesque, RSS Visualizer, Shell, Spectrum and Word of the Day playing directly in Cover Flow mode. Very nice if you ask me!
[robg adds: You can also, as you might expect, use Quick Look on a Quartz Composer file and watch the animation in a larger window.]
I'll never understand why Leopard doesn't have a slider to change the size of the icons/thumbnails when in Icon View mode. Keeping the View Options window open is a workaround, but not very elegant. It turns out that switching to Icon View in a Smart Folder search result offers just such a slider. (I hope Apple just forgot to add that feature to regular folders, and we'll see it soon -- or maybe some fancy terminal command to enable it?)
Grab a couple of video files
Create a Smart Folder search for them
Switch to Icon View mode
Enjoy the slider in the lower right of the window!
And like I said, regular Finder windows don't have that feature.
[robg adds: I did a bit of digging with Interface Builder, and you can find the slider in MDResultsView.nib within the Finder bundle. However, I don't think the regular windows are drawn using any of the other .nibs in the Finder's bundle, so I'm not sure where to go from there.]