I have Photoshop and it's good for a lot of things. It's a little work to learn, though.
For simple things like resizing, color correction, etc., I use Irfanview
, an excellent free photo viewer with a number of editing tools.
Another good, fairly easy to use (and also free) option is Google's Picasa
. I used to upload a lot of pics when I had more spare time, and I played around with Picasa's editing features a little bit then, but now I mostly just use Irfanview, or if I want to do something a little more complicated, I use Photoshop.
I've never used the software that came with my camera, not even to transfer the pics to the computer. I just take the card out of the camera and stick in my computer's SD slot. MUCH simpler.