A fun challenge is posted every 2 weeks with results posted. Recommended by Karin Jurick.
This group is reading a book: The Art Spirit by Robert Henrimonth. The painting challenge is devoted to him and his later influence on The Ashcan School. The book discussion will go through Challenge 10. They're on Challenge 2 at this point. Lots of interesting paintings.
An interesting challenge spot. A "word" is posted every Friday. You paint what that word means to you and post it. A link is included to your site or your blog (if you have one). This week's word is "propagate". Interesting paintings of clouds, a bed pollinating gorgeous flowers - the artists' interpretation of that word.
An website that schedules sketching one day a year and invites the world to sketch and submit their sketches of the cities they live in. A site with links to flickr, picasa and other photo websites where everyone's sketches are uploaded.
Intriguing website using "Google Street View" as its source material. Wonderful paintings of various sites around the world. Each project begins on the first of the month and ends on the last day of the month.