Edumacation

I'd like to either read a good book or take a class on networking basics so's I can be more effective at work. Despite having no training in it, I'm the default sysadmin here. Whee! However, work is happy to pay for classes for me (within reason- we likely can't afford to do stuff like getting me certified in anything.)
There's a class on Windows Server 2003 via the Science Museum, and while I'm sure a lot of the basics are the same, we have a Mac server and a hybrid network.

Any suggestions, O Geek Friends of Mine?