You can install and use SSRS on SQL 2005 Standard. There are couple of features that may not be available to you with standard edition - see here for details: http://msdn.microsoft.com/en-us/library/ms143761(v=sql.90).aspx
You can configure SSRS in standard edition.. Two features related to reporting services (Data-driven subscriptions and Report server scale-out deployment) are not available with standard edition...