Arch is best
Easiest way is to mount it manually. First you'll have to find out which device it is. Plenty of ways to do this, using "fdisk -l" in terminal, gparted, etc. It will be something like "/dev/sdc1". Once you know this, you need to create a folder to mount it. Something like:
Now, you need to mount it (after you've chosen to mount on the phone). To do this:
mount -t auto /dev/sdc1 /media/nexus
auto is the file system, you can type fat32 also but it can figure it out. Then the disk location, then where to mount.
You may need root permissions or changes to the sudoers file to do these. Type "man mount" or "man command" for just about every commands manual. I'm on the phone so I can't write up anything much better than that.
Also, the arch Linux wiki is an invaluable resource, make the most of it.
Device: Galaxy Nexus i9250
Previously: Nexus S i9023