Shaun Ewing has posted detail of a pdf he's written for integrating Cisco Call Manager & Asterisk:

Okay, I've whipped up a little guide.

It assumes you have a working oh323 configuration on Asterisk. I'd appreciate any feedback.

It's not all that well laid out (I created it in around 10 minutes) and some if it (dialplan, etc) is specific to my configuration (four digit extensions, phones starting with 7, system features in 88xx and 89xx), but it should be enough to go by:

http://asterisk.edropbox.net/ccmasteriskvm.pdf

-Shaun