This might be of interest. I wrote four articles for LotusUserGroup.org on how to develop BlackBerry MDS and BlackBerry JDE applications.
Granted the source system is Lotus Notes, but since I'm using web services and 'push http' services, this might be generic enough to get started with.
Anywhoo - 20,000 words of 'getting your feet wet':
Mobilizing Domino Applications onto Blackberry Devices
Hope it helps,
---* Bill
http://www.billbuchan.com
http://www.hadsl.com