Evan had been asking the other day about tools or setups for OS X to send mail while wandering around various networks. Mac OS X has sendmail built in, of course, but there are some niceties about configuring it, especially on a laptop where you are connecting to different networks.
au seems to do a number of interesting things that might fit the bill:
au is a packaging of SMALL BEAUTIFUL tools that allow you to be more autonomous on a network. This version includes a number of Daniel J. Bernstein's utilities including djbdns, qmail, and daemontools. The effect of this combination provides you with a DNS cache and Rendezvous-based email.