An extreme urban sport requiring no equipment or tools other than your own dexterity. "Spidermanning" is the best word I can think of for it, but the official term is "Parkour" (thanks arn). More on Parkour here on LF.  
 
I must admit it has a certain appeal, but that's probably because only an idiot would consider doing this.  
 
Thanks, zf. Opens to embedded wmv with music. NSF Anyone without adamantium knees
Not Spidermanning. Parkour.
arn: This video is of one of the sport/arts originators, David Belle. He is a truely amazing athlete. If you want to see more parkour/free-running videos, pictures, or to get in on the scene yourself head to www.urbanfreeflow.com
DonkaWechico: Thanks for that! I'll update the description, but keep the title so that other ignoramus's like myself get the idea.
DonkaWechico: Thanks. I'd already posted your post, Linus, but now I've included the others. This is crazy!
Look...
scilec: If I had one shot, one opportunity, to try one of those stunts, I'd end up dead or in the hospital. Amazing.