Can you use a bluetooth keyboard with Blackberry?

Yes you can. Check Sponsors link and find Freedom Input Ltd.

I am using the ThinkOutside Stowaway Shasta bluetooth keyboard. Search the forum for members' feedback on which one is best for you. Check with Sponsors if you have any issues if you can't find anything in the threads.

Wirelessly posted (Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0) BlackBerry8830/4.2.2 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/105)

We have a couple of the Shasta's as well, the the users love them.

The BT keyboards work great. The biggest problem is if you are on a BES OR if your BB has ever been on a BES and has keystroke injection blocked. No "Remove IT Policy" process will remove that restriction. If you're on a BES that has the restriction then you have to get your BES admin involved in helping you allow the keystroke injection.

If you are just on BIS and your BB has NEVER been on a BES with that restriction then the BT keyboard is awesome. I love mine.

Just to confirm that the Freedom Universal keyboard works well with Blackberry devices provided, as John has mentioned, there are no issues with the Blackberry Enterprise Server.
We are a Blackberry Alliance Partner and we are there to help if you need any support.
Which model BB are you looking to use a keyboard with?

I tried BT keyboard ThinOutside with 8310 Curve but does not work. do you know why ? Thanks - max

Could be lots of reasons why it doesn't work. What steps did you follow and what were the results?