yes it is possible:
on your web / file server create home directories (after adding a huge hard drive) and EXPORT the /home directory with NFS... on all other machines mount the remote homedir as your home:
one thing though: you MUST make sure that all the "different" users have the same id on every single machine. this was once done with NIS/YP and is nowadays solved with LDAP. since your're running mandrake linux, using LDAP-PAM shouldn't be that big of a problem, it is actually fairly easy.
the LDAP server could be your web/file server. oh, and don't forget to backup frequently, because once the HDD on the file server dies, all home directories are gone banana... since you have multiple machines, you could write a simple backup mechanism that tar-gzips the homedir and copies it onto another machine to, e.g. /var/backup/ - frequently - daily - overwriting the odd days...
- tar.gz /home
- copy to machine2:/var/backup/`perl -e '@a=localtime; print $a%2'` (odd, even day)
this way, the loss shouldn't be dramatic - two days of backup is sufficient (for home use - at least I think so)