Sketching St. Louis is a sketchblog about just that.
Artist and illustrator Michael Anderson found his inspiration for the blog from a workshop he led in 2009 called Sketching St Louis, in which he carried forward the approach found in the Urban Sketchers blog.
Anderson’s sketches of various subjects in and around St. Louis are done primarily in pen and watercolor, and occasionally digitally on an iPad. You can see him working as the subject of a video by Joel Anderson called Urban Sketching.
Though he mentions Urban Sketchers more than once, he doesn’t appear to be a contributor to that blog as far as I can determine, but does contribute to the Flickr pool.
Anderson also has his own Flickr stream.
You can see more of Anderson’s professional and personal work, including architectural illustration and plein air paintings, on his website.