Spell checking an entire website.
Just thinking off the top of my head I can envision a marriage of wget and aspell that would work well. Wrap it all up with a bit of Perl or Python and your good to go. Now this solution wouldn't be as comprehensive as some of the payware stuff but it should be good enough to chunk though the majority of your pages finding blatent spelling errors. Heck, you could probably even get it to do some light gramatical checking while your at it. I think I saw a post on Hacker News about a site that gathers ideas and puts them into peoples heads. Maybe I'll try to submit this one. It's small, simple and pretty much self contained. Perfect!
== UPDATE ==
I found out that the is named JustHackIt and I have posted my idea. Let's see if anything comes of it...