OS X Hints reader AlbertHall found a simple—if counterintuitive—way to retrieve items you want to pull out of the Trash:
Open the Trash folder, select the item or items that you want to retrieve and hit the Delete button (red circle with line through it) in the toolbar. (If you don't see that button, go to View -> Customize Toolbar and drag it from the palette of available buttons to wherever you want to park it.) The item will disappear from the Trash and reappear in its original folder.
As one Hints commenter observed, using the Delete button as Remove From Trash isn't the most intuitive user-interface choice Apple has ever made. Others pointed out that you can do the same thing by selecting the item then selecting Put Back from the File menu; you can also implement Put Back by selecting the item, Control- or right-clicking on it, then selecting Put Back from the contextual menu, or by selecting the item and pressing Command-Delete. Finally, if you delete something accidentally, and want to get it back, you can also press Command-Z immediately to undo the trashing.