Turn off the new window animation in Mac OS X 10.7 (and higher), new windows will appear instantly without delay.
10.8
Disable ‘Home Sharing’ options in iTunes
Disable the Home Sharing functionality within iTunes 7.1 or above. After applying this command the option ‘Home Sharing’ will disappear in the navigation bar and the Advanced menu options.
Show icons from hidden application translucent in OS X Dock
In Mac OS X you can hide an application with the key combination cmd⌘ + H. That the application is hidden you can not see directly in the Dock. Using this command, hidden applications are displayed with a translucent icon in the Dock:
Enable the Safari debug menu
Safari has a hidden Debug-menu that offers some options for debugging the browser. The debug menu is different from the Developer menu. You can perform load and stress tests en additional logging features.
Change default Mac OS X screencapture file type
Specify what file format you want to use for your screenshots (shift⇧ + cmd⌘ + 3) under Mac OS X. Th default format is .png, there are a lot of additional file formats available: png, pdf, tiff, pict, jpg, bmp, gif, psd, sgi and tga.
Change the default location for screenshots in Mac OS X
By default, screenshots (cmd⌘ + shift⇧ + 3) are saved on your desktop. It is possible to change this default location of screenshots, use the following command:
Hiding the files on your Mac OS X desktop
If you’re using your Mac in public, you might not want everybody to see the mess on your desktop! You can run the following command that will hide the icons from you desktop.