I guess it depends what you want to do with your photos, if its just stuff like cropping, and contrast & some of the simpler things like turning to monocrome then freeware like these are a good starting point
http://picasa.google.com/
http://download-photoscape-free.com/
http://www.gimp.org/
out of the three I use photoscape more than the others
I do have paintshop photo & adobe lightroom , which I use on odd occasions , adobe elements is a decent one for applying filters over photos , but I didnt buy after the trial ran out on that one & its no doubt been superse