Anyone interested in Urban sketching should also know about Parkablogs. Teoh Yi Chie reviews books, materials and occasionally has fun videos.
BTW, until November 11, Parkablog has gotten a 50% off deal on several great craftsy classes — you might want to click through FROM HIS PAGE to buy them! I heartily endorse Holmes, Reddy and Blaukoft! (I haven’t taken Heaston’s classes; he may be very good too.)
If you don’t know what Urban Sketching is, video below: