Is there a program equivalent to lint for LaTeX?

Yes, ChkTeX and lacheck. (You probably already have it: if you're using AucTeX on Emacs, when you hit C-c C-c to compile, type ChkTex or Check (for ChkTex and lacheck respectively). Or else, at the commandline, try lacheck.) Thanks for reminding me of this; I ought to use it more (though it can be very annoying :P).

lacheck and ChkTeX are lint-like things that I have used. check, which I have not used, also seems to provide syntax checking.

Below is a link to a package that provides style checking for latex source files.

http://www.cs.umd.edu/~nspring/software/style-check-readme.html

It will find common latex typos (e.g. " instead of ``) rather than overt syntax problems. It also comes with a set of rules to detect common grammar mistakes.

I used it (with some modifications to the style rules) on my thesis. I found it most useful to enforce my own spelling rules and standardize some latex constructions.

It's pretty easy to customize, which makes it handy; though I haven't used the other suggestions so I don't know how easy they are to customize.