Feeling trasher's remorse? On Snow Leopard, you can open the Trash (click the Trash icon in the Dock) and "untrash" individual items there. Select one or more trashed items (files and folders) and choose File > Put Back. This returns the items to where they were when you originally put them in the trash. The keyboard shortcut is Command-Delete - the same as the shortcut for trashing an item in the first place, since in deleting something from the trash you are untrashing it.
From Matt Neuburg