Messenger

csm.gif If you’re familiar with WinPopup (which, there are few people that are not due to the funky exploits on the Internet that access this very annoying little popup window), then you would know exactly what Messenger is capable of. Used as a replacement for WinPopup, you can send messages, receive them, filter, autoanswer, and a whole gaggle of other features that you probably really don’t care about.
Interestingly enough, if you need something quick and dirty to message back and forth, this will do the trick nicely. Free for Windows.