Freeware: Aspell

CocoAspell 1.4.2 Aspell is an Open Source spell checker designed to eventually replace Ispell. Its main feature is that it does a much better job of coming up with possible suggestions than Ispell does.

Free Spell 4.0FreeSpell is a spell checker for any and all Windows applications. You can use it in Eudora, in Microsoft Outlook, Symantec Visual Cafe, and even in Windows Explorer when renaming files (though it's a little tricky to do that).