There's an excellent Excel spreadsheet created by Kenad Broki from the
WotC boards, which is currently being maintained and updated by Ben/NotLestat. Covers the current errata as well as material from all the sourcebooks.
You can find the main thread here:
Don't call it a generator, but... - Wizards Community
The latest version is 1.29d, and can be downloaded directly from here:
http://www.mediafire.com/%3Fmwmwjjjnyyx. Bear in mind that it's not 100% bug free, but there are several folks at the
WotC boards, including NotLestat himself, working to correct as many of the bugs as possible. But as long as you keep this in mind and don't take the final stat block as 100% gospel, it works pretty well.