You can iterate your database list with a cursor or procedure or however else you want and use that query to list out the queues. Any row that is returned from that query is a queue in that database.

You can also inspect messages in each queue; with a select * from the name of the queue in the above query. The name of the queue doubles as a kind of table name you can read messages from. A select is safe; there are other commands to pop messages off the queues permanently.

I'm not sure what else you're asking but there are quite a few videos around on how service broker works (and one book for 2008) that can explain it in more detail.