Practical spell checker: aspell

aspell is a practical spell checker available for Linux and Mac OS X. It is installed by default on most linux distros. You can get it in mac using MacPorts/Fink. aspell goes through your document, asking to replace words that it suspects are wrong.

I used it a few days ago to spell check a paper of mine before submitting. It has different modes, for instance a TeX mode. Here is how you call it to spell check a latex document written in english:
aspell check -l en --mode tex paper.tex

How to spell check a document in brazilian portuguese:
aspell check -l pt_br test.txt

Try it, it is very easy to use.