Well of course Photoshop is the "standard", although pretty expensive for casual use unfortunately. But you can usually get Photoshop Elements relatively cheaply... manufacturers used to include an older version for free whenever you bought a scanner. I haven't used the newer versions, but the old one really had a nice feature set.
Does your camera support RAW mode for photos? If so then you get a lot more control afterwards, but you will need software which can use that format. Not sure what inexpensive programs support that, but I'm sure there are some.