Mandiant had some interesting presentations about IOC and released the free tool IOCe to create them. There's also a forum about OpenIOC.
State of the Hack: ABCs of IOC (May 24, 2010)
Fresh Prints of Mal-ware: 0x1,0x2,0x3s of IOC (Aug 26, 2010)
Lots of other interesting things to talk about... as soon as I find time to write more :-)