Since you've moved to 2008, I'd strongly suggest you start taking advantage of the new functionality available there. To see who is currently on the system you can query the dynamic management view (dmv) sys.dm_exec_requests. If you filter it by adding to the WHERE clause SESSION_ID > 50, then you'll also eliminate the system connections, which will keep you from seeing stuff like the checkpoint queue.
There is a lot you can do from the dmv, including connecting it to other dmv's to get the query being run, execution plans and all kinds of other information.
