As the title says, here's how to mount Linux partition in OSX:
1. Download MacFuse .dmg from http://code.google.com/p/macfuse/
2. Download fuse-ext2 .dmg from http://sourceforge.net/projects/fuse-ext2/
3. Install them respectively.
4. Reboot your computer?
5. Here is the magic terminal keywords to mount your beloved Linux hdd:
a. First do: 'disktool -l' to find out the name of Linux hdd you're interested in. The name is something like disk0s1 or similar.
b. Next: 'mkdir /Volumes/[HD NAME]' replace HD NAME with your choice of your name. (eg. Linux)
c. After that, 'sudo fuse-ext2 /dev/[LINUX HD NAME] /Volumes/[HD NAME]/ -o force' replace the LINUX HD NAME with the name from part a. above and HD NAME from part b. above
Voila! You're beloved Linux partition is now mounted! :)
Tips: You can add a script to your .profile to automate the steps above every time your computer boots up!