Check-It

From CDH Productions:

Check-It is a fast, powerful, configurable, and very intuitive stand-alone spell checker and thesaurus with many more features than comparable products. You can do a normal check, batch-mode, quick check, or even check text in other applications. A complete 30,000+ entry Thesaurus module is also present in which you can check any word (Noun, Verb, Adverb, Adjective, etc.) in your current document or a new word in a separate window. The normal spell check brings up a window that displays the misspelled word, suggestions, and the document context, so you don't have to worry about the window getting in the way of your document. The Batch mode displays a list of "misspelled words"; simply double-click a word in the list to advance to that word in your document. The quick check module provides a fast, easy, and convenient way to check spelling. You can also minimize the application to the system tray for very convenient access. There are several options you can choose from to customize your spell checking such as ignore, catch double words, auto correct, suggest split words, and much more.