Tucson has some great muralists. You can find them here every couple of days or by searching local news (see our December 15, 2011 post for some suggestions).
Outside Tucson, Google follows the latest mural news. Check the "Murals in the News" section in the right-hand column of this blog.
I've seen some great websites and blogs with street art from around the world; one I found today is StreetArtNews.net. (The home page keeps getting longer and longer as you wait. You might try clicking there, then going for a cup of coffee and waiting a few minutes before you scroll down.) Don't miss their wraparound mural in Namibia — and imagine going past it yourself as drive around that corner! (Reminds you of Eadweard Muybridge's animal locomotion photos, doesn't it?)
There's a new building along the Thames River in London called The Shard. The 360-degree view from the top is like a non-stop mural.
If you have any favorite mural sites, you can share them by leaving a comment at the end of this post. Thanks.