also
www.sosketchy.blogspot.com
it's new.
kristina's and many others are all blog posts. if you just subscribe to the site either by email or an rss reader (try google reader, owlrss, sage, yahoo, blogline, etc.) you'll get an auto email or it'll pop in your reader when the person post. so you'll never miss anything as long as you check your email/reader regularly.
there are tons of challenges. i try to rotate even though my favorite are color challenges. i do sketches if the sketch feels right. colors give me more freedom in terms of lo.
i do find mojo monday, caardvark, and so sketchy very nice for sketches.
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