Mapping around SW London mostly. Done most of Wandsworth and Fulham with my flatmate Andy.

I do the cycle map with Andy:
http://www.opencyclemap.org/ (and also the third layer on the www.openstreetmap.org site these days)

Other stuff I'm involved in:

No names map (highlights streets with no name):
http://dev.openstreetmap.org/~random/no-names/

Progress images (shows regions in OSM as snapshots over time going back into the OSM dark ages):
http://dev.openstreetmap.org/~random/progress/

And you can blame me for some of the relations handling code in Potlatch too!