user connections ,Logical Connections, Threads, Logins , Logouts

select *
from sys.dm_os_performance_counters a
where a.object_name = 'SQLServer:General Statistics'
and counter_name in ('user connections ','Logical Connections','Logins/sec','Logouts/sec')

--Number of threads used with MSSQL 2005

select count(*) as 'Number of threads'
from sys.dm_os_waiting_tasks
where wait_type <> 'THREADPOOL';