Multiple LINUX OS's, same filesystem & accounts?
 

is it possible to share the filesystems and the passwd file with multiple LINUX OSs? I know you can mount /home seperately, and mount the OSs seperately, and I am doing so, but sharing the same logins with each OS?

You might want to look into using NIS+ or one of the other methods of centralized account management.

As far as sharing partitions, you will want to read through the Linux Filesystem Hierarchy Standard publication on the net. It goes though what can be shared, what can't. Which partitions should be static, etcetera.

It also gives a rational for each recommendation.

You can find the LFHS here:
http://www.pathname.com/fhs/