Last week I have found somewhere on the forums trick how to instantly grab a part of the screen on Mac OS X. It left in my memory, and I had no idea at that time how handy would this be. Just press Cmd-Shift-4, and  there appears a new cursor which allows you to select part of your screen, and saves that screenshot to png file on your desktop.

The second trick allows you to magnify part of the screen under your cursor. It is a new feature of 10.4.8. This was also very handy during the development of the new Vortex database editor. Just press ctrl, and scroll you mouse wheel. Screen smoothly zooms in and out.