At work we have had a nightmare with our e-mail server because of some corrupted data with the domain name registrar. We changed some e-mail addresses and decided to use Google Apps for e-mail. It was pretty painless with Dreamhost setting up everything with one click.
Basically it is free if you are using under 200 users. It includes 7 megs of space for mail, a calendar, Google Docs, Sites, and Google Talk. Everything works within your own domain and it was pretty easy to setup. There was only a couple of default settings we changed for Google Sites.
It’s free and so far the staff love it. As far as training, I think it will be about 10 hours for 30 users which includes setup. If you are running IT for a church, a non-profit, or a small business, it seems to me to be a pretty obvious choice for all of your web needs and the price is sure right — free for under 200 users.