Panasonic GX1 body only goes for $265 right now and with power zoom 14-42 X lens, is $499. It may be 1 generation old, but will be much better than the compact options the OP listed, as well as being more flexible with glass. The Panny 45-175 X lens* is very compact when compared to its APS-C analogues, and produces very good image quality in an extremely compact package (I borrowed one from a friend and fit it easily in my inner jacket pocket on a zoo trip). If you want even more reach (eg going on safari) there's the panasonic 100-300 lens or the Olympus 75-300, giving the equivalent FOV of a 600mm lens on a full frame body.
Much smaller and lighter than the 5D, much more versatile than a compact, and at a price that's hard to turn down, this would be my pick for a small, powerful photographic tool on a budget.
* EDIT: One annoyance I had with the 45-175 X is that it resets the zoom to 45mm every time the camera is powered down; this may not bother you depending on your shooting habits, but I'm pretty fastidious about saving battery between shots. Because of this, I tend to get double the CIPA shot rating of my camera (800 shots on my GF1 out of a rated 400 for the battery - useful if you're in the boonies). Still, if you can find a good deal on the lens (my friend bought his new for ~$150), it's a great little lens.