Something else you can try, with /home mounted, do (as root):
du -s *
That'll show you a summary of how much space each directory inside /home is taking up. If there's a really big one, go into that directory and do another 'du -s *' to see if the space is being eaten up by some directory inside there... repeat until you figure out where all the space is going
You can also use the 'find' command to locate excessively large files, but the space might not be in large files. Try this, though:
find /home -size +10000k
That'll show you anything more than 10MB in size. You might also want to look for core.xxx files, since those get dumped whenever a program crashes. If you see anything called core.12345 or such, delete them immediately. You can use find to locate those also:
find /home -name 'core.*'