WPKG takes care of the WSUS and group policy-style updates, silently, efficiently, centrally, and works with samba! wpkg.org. We use this across multiple states in a multi-location medium sized business.

Not free, but IM+ provides gateways to all major networks, including Jabber. I have it set up to connect to my corporate server (running openfire). Support is excellent, and it's a one-time fee of $50. I have been upgrading for 3 major versions now. They are adding features / interface improvements all the time.

O'Reilly Safari Bookshelf has been a lifesaver.
Start on one package, read up and learn about the first service, then start on the next.
A commenter further down calls them 'glorified man pages', and a man page is an excellent place to start, but O'Reilly goes far more in-depth with topics like security, concurrency, etc.
Can't recommend them enough!