On www.mssqltips.com you can find my latest tip Report launcher to run SSRS report subscriptions on demand.
SSRS Subscriptions are great feature, but if you would like to run the subscription on demand out of the predefined schedule, it can be a tricky and you will start to dig into the SSRS database and agent jobs.
The tip describes, how you can easily create a set of simple SSRS reports, which allow very easy on demand launching of subscriptions.