You know, if you're tired of the endless leveling just so you're running in place, try something else:
Second Life
www.secondlife.com
This MMOG lets you create your own objects, upload your own textures, and even has its own scripting system to let you program your own objects to do things. How cool is that?
I've been playing it for the last couple of weeks. Unfortunately, the requirements are pretty high- you need 500kbps of broadband, and at least a GF3 or so. Did anyone see this at E3?