Keynote: Turn off Spell Check; Unusual Uses for Keynote
To turn off auto-spell check in Keynote, just go to Edit > Spelling and uncheck "Check spelling as you type".
Why would I want to turn this off? I use Keynote to quickly make graphics for blogs, websites and even for my presentations and reports. I draw or compose the image in Keynote and use Keynote's handy effects (shadows, reflections, etc). Then I take a screen capture of it (using Cmd-Shift-4) and use the file!
Anyway, sometimes I use proper nouns, brand names and non-English words. Auto-spell checker underlines these in red. Since I don't want this to show up in the final graphic, I turn off the spell checker.
That's two tips in one blog entry! :)