Find SQL Services running on a Instance

dm_server_services is a useful system view which provides detail about SQL Services running on a instance and other good feature is that it shows even the cluster node on which SQL Server services are running.

Query
SELECT servicename, 
  startup_type_desc, 
  status_desc, 
  last_startup_time, 
  service_account, 
  is_clustered, cluster_nodename
FROM sys.dm_server_services

Output 
servicename,startup_type_desc,status_desc,last_startup_time,service_account,is_clustered,cluster_nodename
SQL Server (MSSQLSERVER),Automatic,Running,2013-05-31 23:31:38.7849183 -07:00,domain\user,N,NULL
SQL Server Agent (MSSQLSERVER),Automatic,Running,2013-05-31 23:31:46.0190158 -07:00,domain\user,N,NULL