Memory Supervision System

http://hem1.passagen.se/blizzar/mss/index.html - original MSS home page. It hasn't been updated for a long time.
http://www3.hmc.edu/~neldredge/yamd/ - Yet Another Malloc Debugger home page. This one use OS/CPU specific methods for detecting out of bound accesses, so it may catch more bugs than MSS at the price of very limited platform support. Currently it works on x86 processors running Linux and DJGPP in DOS (not Windows).