SQL Server 2008 R2 Express for a single website?
You do not need the SQL Server Agent. It has nothing to do with database connectivity.

http://msdn.microsoft.com/en-us/library/ms189237.aspx


  SQL Server Agent is a Microsoft
  Windows service that executes
  scheduled administrative tasks, which
  are called jobs. SQL Server Agent uses
  SQL Server to store job information.
  Jobs contain one or more job steps.
  Each step contains its own task, for
  example, backing up a database. SQL
  Server Agent can run a job on a
  schedule, in response to a specific
  event, or on demand. For example, if
  you want to back up all the company
  servers every weekday after hours, you
  can automate this task. Schedule the
  backup to run after 22:00 Monday
  through Friday; if the backup
  encounters a problem, SQL Server Agent
  can record the event and notify you.