Maybe a bit different than the London you're used to seeing, but London, nonetheless.
Derelict London
Check out the abandoned railway line in particular, and think what a little renovation could do to that area. Love the Green Man sculpture coming out of the brick wall! Also, don't miss
cemeteries,
murals (the Shoreditch one is hilarious,) and
hospitals.
Part of Yahoo! UK's people's choice awards for best finds in 2004.
If you're a New Yorker rather than a Londoner, there's a similar site, Forgotten New York. It's more extensive than Derelict London, and it looks like they've got three new photo galleries to explore for 2005. I can't quite decide which one to explore first.