It seems that the best tool on the market is GNU aspell and it supports TeX. However, it's very difficult to configure it right. I made my own texsc tool to simplify the usage of aspell. You just do this and your LaTeX documents will be checked:
gem install texsc texsc --ignore=citet,citep,verbatim book.tex chapter1.tex chapter2.tex You can also specify your own additional vocabulary:
texsc --pws=vocab.pws book.tex More info in this blog post of mine.