The one I’d recommend using is:
Here you can access the order details as well as shipping etc.
This is how it’s called:
Mage::dispatchEvent('sales_model_service_quote_submit_after', array('order'=>$order, 'quote'=>$quote));
In line 210 of app/code/core/Mage/Sales/Model/Service/Quote.php
You can also look at:
A list of events can be found here...
Hope this helps