I bought myself a BlackBerry 7100 a few weeks back. At the time someone said you could add it to iSync using PocketMac.
I got around to looking into this yesterday. Talk about great timing. At Mac World 2006 San Francisco RIM announced they had licensed PocketMac for all BlackBerry users.
While it was announced that the free version would be up on blackberry.com in February, you can download it now from PocketMac. They have changed the price to $0. Make sure you use the credit card option. It will skip the credit card screen and take you straight to downloads. If you use PayPal it causes an error. Obviously the store is not normally used for charging nothing.
PocketMac seems to work fine as an iSync conduit.
Now if only I could something working for Lotus Notes syncing to iCal…