Ok - got this all working now. Here's what I had to do (since it's a bit involved)
The real key is DavMail. Configure it per the URL above (http://www.brucerenner.org/linux-and-exchange-2007
If you're doing Thunderbird and Sunbird, you're done. If you're trying to stick to the Ubuntu provided stuff (like me) you might have more luck with Evolution.
Under Evolution, do *not* configure the exchange stuff, and remove it if you have (it fights with DavMail, or did in my case).
1) Set up the IMAP server just like you would Thunderbird. If you're using AD and your username and email/box names don't line up, just set them as needed.
2) Set up the SMTP server like Thunderbird.
3) Under the calendar section, create the new calendar, select WebDav, and proceed like Thunderbird.
Very easy, works pretty well, and is integrated properly with the Ubuntu notification app and all.