Haven't seen much interesting graffiti (which I want to start calling "underground street art") while out-and-about the town, though recently I came home and found my front porch decorated in a lively fashion:
This artwork was done by my housemate Jonah, aged 2 (and his momma, Katy) on behalf of another housemate, Josh, was recently released from 30 days in lock-up for his part in a Greenpeace action.
I particularly like the stars on the faux-sky blue porch. Truly ingenious design.