The forum and articles at
www.msexchange.org are good.
If you can, download the 120 day eval at Microsoft's website and install on a test server enviroment to play around with. You should do this on its own domain probably. I doubt you can still get the 2000 version this way, but you can probably download the eval of 2003 still.
Some books I have found helpful:
Exchange 2000 Pocket Guide This one is useful as a quick lookup / desk reference. It gives you the general quick explanation of different topics and troubleshooting.
Exchange Server 2000 24/7 Very easy to read and help to analyze install and some good troubleshooting.
Also, check out Microsoft TechNet, which can be a very good reference for free.