Oh yeah, didn't realise you could edit images in Photobucket. If you want to do it that way just click the edit button above your image then Resize Image. In terms of editing software, I'm not sure there is any decent freebies on the web unless you start getting all illegal with file sharing, but obviously I don't encourage such things
Photoshop is pretty much the dogs nuts, but takes a little bit of time getting used to. You might have some basic Microsoft Picture Manager if you've got Office installed on your PC.