On top of the resources that you listed, I have found these two sites to be incredibly useful:
- peeron.com - Large set database and instruction scan library
- bricklink.com - Lego marketplace selling millions of used and new parts and sets. This is also a nice reference for information and inventories related to old sets.
It's not a site, but if you don't mind books, I would recommend The Cult of Lego by John Baichtal.
You also might be interested in finding a LUG (Lego users group) near you. Here's a map.