Email is frequently used at our library. Some of our content we are in the process of moving (or duplicating) to a wiki. It's all about organization - so much communication here becomes a reference for later. (You know, I had a problem with such and such patron/couldn't get the microfilm scanner to work....how do I do this??)
I personally use IM frequently at home with friends who are long distance - it really helps us keep up with eachother since so many of us seem to use computers/internet to relax or manage personal finance.
Two interesting communication tools that I have seen are:
Also be aware that if you use iGoogle you can share documents and work on them with another person (or multiple people). Neatest tool ever that I haven't been able to use yet. But if I could...oh boy!