You could try:
http://www.cloudynights.com/ubbthrea...oard/Sketching
And:
http://perezmedia.net/beltofvenus/archives/000567.html
There is also ASOD (sketching's APOD):
http://www.asod.info/
The first link in particular will, if you go to the trouble of searching the back entries, give pointers to how people sketch and their various techniques and tips.
The second link has a heap of resources and pointers to further info.