Ubuntu Servers :: Replacing Home Network - Central User Management Setup?

I am replacing a home network - Windows Server 2003 and 5 PCs (XP Pro) with UBUNTU 10.4 LTS Server and client versions. I am keeping a couple of the PCs with dual boot until I can migrate everything over (Having some issues with iTunes, Family Tree Maker, Media serving, DVD decrypt and a couple of others, but that is for another post). It was great fun getting the server up and running using only shell commands. Took me ages just to get a folder shared! Migrating the data over from NTFS to ext3 was also fun given the limited space on the partitions.

I really only want to use the server for communal network type things ... central user account maintenance, shared folders for music, video etc and data backup. I don't need it to be performing server functions on the Internet e.g. web server etc although that may come later. How I set up central user management? All the PCs are currently setup with local user ids, and it is a bit of a pain to go round each PC every time I change something.

The server is not always up, so I need to be able to log into the local PC without it being active. I was using Active Directory on Server 2003, but I don't need anything that complex really ... just 3 or 4 users to manage. I have been looking at the setup tutorial at [URL] but am not sure how relevant a lot of it is. I have SSH setup so I can login remotely, NFS is working to share the folders, but that is about all I have done so far.