Macmaps has a great FAQ page on ways to speed up Mac OS X.

Ever have a burning desire to freeze a window while it’s minimizing? Here’s the scoop:
Open up a terminal window (Applications -> Utilities -> Terminal.app) and without hitting enter, type:
killall Dock
Now switch to an application window (Safari for example) and minimize the window in slow motion (Shift+Minimize).
While the application is minimizing, switch back to the your [...]

If you’re looking for a way to spruce up your menu bar head over to Super OS X Menu Bar Items. This is a great resource for dozens of little icons you can add to your menu bar.
The menu bar is the bar at the top of your screen that has all of the little [...]

The bookmarks bar has become a necessary item on my web browser for the greater part of my computing career (including that barbaric pre-mac period I don’t like speaking of :)). I’ve found it’s the quickest way to access websites you visit regularly.
If your unsure what a bookmarks bar is, here’s a screenshot of mine:

Recently [...]

Save time by scrolling with two fingers. Never click the sidebar again.

Instead of pressing and releasing the key(s) to invoke Exposé or Dashboard, press and hold the key(s).
While holding the key(s) down, do whatever action you set out to do.
After your done, instead of pressing and releasing the key(s) again, simply let go.
While this is a pretty simple tip, I’ve found it to be much faster [...]

To open and select an application in finder, an application in the dock.

Now watch the finder window open in list view with the program selected:

Matt Smith (the tip submitter) says he missed the availability of the Start Menu and found this as a quick and easy alternative. The folder is alphabetized, so by clicking [...]

On August 1st, I launched MacTips to the world. By launched I mean I had the site completed with 9 mac tips ready to be discovered. I e-mailed the great folks at The Unofficial Apple Weblog. I let them know about my site and why I though it would benefit their users.
To my surprise they [...]

When switching networks, it can take anywhere from a few seconds to a few minutes to get assigned a new address. This means you’re checking every few seconds to see if you’re connected yet.
Safari, however, is notified when a new connection is made–and will attempt to reload any pages that failed to load.
This means after [...]

When choosing an application from the dock, press to hide all other applications, and show only the application you clicked.
It sure does tidy up your screen in a jiffy.
[Submitted by Dave]