If you use instant messaging to communicate you should be using OTR. Basically it makes messages look like a bunch of garbled crap to anyone who might be intercepting your traffic. That isn't such an unlikely scenario these days with free wireless being all over the place - bars, libraries, coffee shops, etc. So, instead of seeing;
(2008-09-24 10:35:36) Me: http://www.thewebsiteisdown.com/
(2008-09-24 10:35:37) Matt: lol
(2008-09-24 10:37:25) Matt: that link is better
They'll see
Me: ?OTR: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.
Matt: ?OTR:AAIDAAAAAAEAAAABAAAAwGnhPrS8lds0rHIFKhwlYOFfxyNGWwUp6qAy6b7z/AXlftvgWyRShRZFmza0atUN72lUHLTEzLiepgrtSQvuNCQblgb53R3G6HbP+T+0h/M7MH27FcuVke2o0phHF1lpWENLwZlzc07K8uqo3VNSLQVA8vzyOO9aFZHO7ERdnO37ftNlQDVhKclWl1JjZtIa8h//nNPP1o3BXzRU5og+xw3ZlSmpb6Qe7hAEvJbOEsoGBEhPaVW6PeIqNWO3jepsNQAAAAAAAAABAAAACPFDxCMQUKGNjkWJoe1X7VoFl1cPTz2KSbEsxkEAAAAA.
?OTR:AAIDAAAAAAEAAAABAAAAwGnhPrS8lds0rHIFKhwlYOFfxyNGWwUp6qAy6b7z/AXlftvgWyRShRZFmza0atUN72lUHLTEzLiepgrtSQvuNCQblgb53R3G6HbP+T+0h/M7MH27FcuVke2o0phHF1lpWENLwZlzc07K8uqo3VNSLQVA8vzyOO9aFZHO7ERdnO37ftNlQDVhKclWl1JjZtIa8h//nNPP1o3BXzRU5og+xw3ZlSmpb6Qe7hAEvJbOEsoGBEhPaVW6PeIqNWO3jepsNQAAAAAAAAACAAAAIC60G6RKhlsYl3lX6bLoLEamphgA/20RR1NHoWlvk2/0grXePmV3RGJYQ/amiKpd+YfInD0AAAAA.
That's also what will end up on the servers for AOL, Yahoo, MSN, Google or whichever IM service you use. Yes, they store your old conversations. If you use Google's Gtalk service you can actually view your old conversations in Gmail.
How does one use OTR? If you run Windows, throw away AIM, Yahoo Instant Messenger, MSN or whatever other garbage you're using and install Pidgin (
www.pidgin.im) as your instant messaging client. Install the OTR plugin from
Cypherpunks.ca in the section labeled
OTR plugin for Pidgin. Run Pidgin (close and run it again if you were running it already) and press
ctrl+U to bring up the
Plugins menu, enable
Off-the-Record Messaging and close the window. If you start chatting with anyone else who has OTR enabled, it will automatically start an encrypted session with them.
Mac users can install Adium. It has OTR enabled by default.