OS X tip: spelling suggestions

Thanks to a thread at Ars Technica, here's a fantastic tip for anyone on OS X. If you're using a Cocoa app (Mail, Safari, TextEdit, etc) and aren't quite sure how to spell a word, type the first few characters and press F5 (or Option-Esc). An inline drop-down form will appear with suggested words for you to choose from. A huge timesaver.