I recommend to visit the following websites too:

Pat Harrison ( Great Paintings in Oil and Acrylics)

Andre Jute ( Best Seller Author and Painter)

Russ Stutler ( the semi god of urban sketching)

Matthew Mattingly ( great art by an all weather artist)

Brian van der Spuy ( artist and author)

 Michael Daley‘s very informative website about restoration and conservation malpractices

Discuss about sketching at sketching forum

Graham Beech ( for excellent website hosting and technical support)

Roughpixels for beautiful WP themes and technical support