There's also the Canon Photo Professional that came with your camera, though I find on Linux the latest version doesn't run under the latest versions of Ubuntu and Wine, and it's not that good anyway. Picasa has improved massively since I first used it - almost tolerable though lacking some crucial features. GIMPs the go (out of the freeware options) for anything serious (well, there's a fork of GIMP that's even better (e.g. 16 bit colour) but needs so many other packages first it's practically impossible to install).
And for all the feedback on shooting into the sun, it's actually good that the shot's too bright here because you actually captured the darker areas of your dog's coat and could potentially get a usable picture out of this with a bit of post-processing work. It's hard to get a great picture though: harsh lighting creates sharp lines of light vs shadow that can't be restored in a decent timeframe with post-processing software.
Cheers, Tony