Event Handlers

Difference between workflows and event handlers

1) Event handlers will trigger automatically where as workflows can be in either way.

2)User interaction is not there in event handlers where as opposite in workflows.

3) Event handler run for short duration where as workflows run for long duration

4) Workflows will be avalable after system down(maintainace,IISRESET etc) but this is not possible in event handler

There is no event for site created but site deleting and site deleted events are available.

To handle/run some custom code whenever a site is created.
Create a Feature that has an Event Receiver defined on it and call the Feature activation event.(There we can run code) Then, use a Feature Staple to staple your Feature to the GLOBAL site definition.