I don’t use the Blackberry, but there are people out there who do. For those users, there is now free server software from Blackberry. Mariette Knap has written an precise and clear guide on how to install this server software on SBS2008. There is quite a bit of work involved, and a far cry from what iPhone and Windows Mobile users need to do to get set up on SBS2008.
The guide is free and can be viewed here – http://www.smallbizserver.net/Articles/tabid/266/Id/343/How-to-install-BlackBerry-Enterprise-Server-Express-on-a-SBS-2008.aspx