This query shows all queries executed at the moment, the session id, status, used cpu time and the execution duration

SELECT st.text, r.session_id, r.status, r.command, r.cpu_time, r.total_elapsed_time
FROM sys.dm_exec_requests r
CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS st

The following query shows the number of connections a user has with a database

SELECT db_name(dbid) as DatabaseName, count(dbid) as NoOfConnections, loginame as LoginName
FROM sys.sysprocesses
WHERE dbid > 0
GROUP BY dbid, loginame