If you think Time Machine backs up too often (or not often enough) for your liking, navigate into /System » Library » LaunchDaemons. There you’ll find a file named com.apple.backupd-auto.plist. Open it in your favorite text editor, and look for this section:
StartInterval3600

Change the 3600 number to some other time interval in seconds, and you’ll have changed Time Machine’s backup interval.

macosxhints.com - 10.5: Set the Time Machine backup interval

One of the most popular Leopard hacks removes the glossy eye candy from the re-worked Dock. To go back to the 2-D version, open Terminal and type these two commands:
defaults write com.apple.dock no-glass -boolean YES
killall Dock

Tweak Mac OS X Leopard’s User Interface / Wired How To’s

SSH connections on Mac OS X are sometimes very slow (long delays) although it’s instantaneous on Linux. Modifying an option in the configuration files fixes this injustice.

Fix slow SSH connections (delays) on Mac OS X