Back in August, 2006, Randy posted the story of a mural behind an ugly lot just north of the corner of Speedway and Stone (1122 N. Stone).
Today there's a new mural, but the lot is still ugly:
The mural was painted by Rock Martinez.
Update (May 1, 2010): Here's the same mural at night.
Here's a Tucson Citizen article (December 3, 2009) about the mural: AWESOME Dia De Los Muertos Mural completed on Stone/Speedway!
Update (December 26, 2010): Rock is the owner of the new Art Terrain Art Gallery at 519 N. 4th Avenue.
Update (February 8, 2011): You can read and watch an Arizona Public Media interview with Rock Martinez that also covers Tucson's graffiti problem.
Update (January 1, 2015): Here's the new mural, painted a year ago or so.