Roughly equivalent functionality is built into GCC. Use the -Wall option to turn on most of the useful extra warnings. See the GCC manual for more details (type F1-i in Emacs and select the entry for GCC).

There is a freely available program called lclint that does much the same thing as traditional lint. The announcement and source code are available at on ftp://larch.lcs.mit.edu/pub/Larch/lclint/; on the World Wide Web, look at http://lclint.cs.virginia.edu/.