While recent versions of the MacBook Air ship without Adobe Flash installed, the idea of voluntarily removing Flash from /Library/Internet Plug-Ins got some attention when John Gruber wrote about his technique. Put simply, Gruber removed Flash from its default location, thus trying to force sites to load HTML5 versions of content. For instances when that didn't suffice, he would load the page in Google Chrome, a browser which has the Flash plug-in embedded within it. His add-on trick is to enable the Develop menu in Safari and use System Preferences » Keyboard to map a shortcut for taking a page in Safari and opening it in Chrome.
The underlying logic of such an approach is generally twofold. For one, it helps site developers get a sense of how many folks are viewing pages using Flash-free systems, thus possibly encouraging them to publish content that doesn't rely on Flash. Two, and much more pragmatically, it reduces the system load since Flash on the Mac is known to regularly use a large percentage of the CPU, sometimes even after the user has closed the window (or tab) where Flash content was viewed.
Should anyone pursue a route like this, Google Chrome is obviously an option for when content is only available using Flash. I tried that for a while, but for subjective reasons I didn't much like Chrome, mostly because of its lack of support for system-level features (e.g., the built-in pop-up dictionary), large footprint, and auto-updating behavior. So I went hunting for alternatives. Here's what I've found that works:
InDesign CS4: Perhaps earlier versions have it, too, but this version of InDesign has a Flash-embedded version of Opera embedded within it (I recall it was version 9.x of Opera). I can't speak to the current version of InDesign, now at 5.5, but standalone version 5 does not have Opera. Perhaps it's only installed when a full Creative Suite installation is performed.
OmniWeb (currently v. 5.10.3): Right clicking on this application and choosing Show Package Contents will reveal a PlugIns folder. Simply move or copy the Flash plug-in here (even the one embedded in Chrome) and this browser will handle Flash content.
iCab (currently v. 4.8): This is my personal preference. It has the leanest footprint of the options I've found, and it easily imports (or just uses) things like Bookmarks, History and Cookies from Safari. While it doesn't have a Plugins folder embedded within it, simply creating one called PlugIns with a copy of the Flash plug-in will work.
Perhaps there are other browsers which can be used, but my tests with SeaMonkey, Camino, Firefox, Shiira, Sunrise, and the current Opera (v 11.10) were not successful.
[crarko adds: I tested this on a few of the mentioned browsers, and it works as described.]
Mac OS X Hints