Since you didn't specify a version, I'm going to reply based on SQL 2005. You best bet is tables in the MSDB database that are named dbo.sysdtsxxxx - these tables hold all the package execution details. Specifically, dbo.sysdtslog90 gives a good basic history of package execution.

SELECT [id],[event],[computer],[operator],[source],[sourceid],[executionid],[starttime],[endtime],[datacode],[databytes],[message] FROM [msdb].[dbo].[sysdtslog90]

And dbo.sysjobactivity should show any currently executing packages.

SELECT [session_id],[job_id],[run_requested_date],[run_requested_source],[queued_date],[start_execution_date],[last_executed_step_id],[last_executed_step_date],[stop_execution_date],[job_history_id],[next_scheduled_run_date] FROM [msdb].[dbo].[sysjobactivity]

Another useful table is dbo.sysdtspackages90, which will give a listing of all your stored packages. Note that there is also a table named dbo.sysdtspackages, which is used for compatibility with legacy DTS packages.