When chatting with a Jabber contact using iChat, you can use IRC-like /me syntax to perform actions. For instance, typing...
/me wants a Napa-based PowerBook with a
dual-core Pentium D, a 533MHz FSB, DDR2 RAM and SATA II.
... will produce this output:
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050613130357866