I have been using zterm on my mac for years and was upset to find that when I upgraded to Lion it wasn’t going to come with me. It is a simple no nonsense console utility that works well with my Keyspan USB to Serial adapter. After looking around though the author has updated it to be a universal binary which can be had here:

http://homepage.mac.com/dalverson/zterm/

Great application for a great platform. If you use it and you like it, flip the author some coffee money and let him know how much you like it.