if you search this forum you should find an old thread where i had a link to a program that can mount EXT2 and 3 partitions. it can't fully mount EXT3 it mounts it as EXT2 so you lose journalling but it works read/write. if you just want to run linux inside of windows qemu works well.
edit: as i recall i also found a program that worked for OSX as well, never tested it myself but macdude said it worked. i'll see if i can find my old thread.
edit2: linkage my friends. i don't know if you can still get the program but if not contact me and i should be able to send you an old version.
http://tech-forums.net/showthread.php?s=&threadid=75108