Yep it does depend.
I started off using Picasa. It's free and easy for basic fixes, cropping, light adjustments and not bad for sorting photos.
As time went by I started using Adobe Photoshop Elements (version 6) where I learnt a little about sharpening, layers, levels, cloning and the likes.
I have now discovered the delights of shooting in raw and am currently using a demo version of Adobe Lightroom which I really like. Bad idea installing this demo as I have a bad feeling when the demo license runs out I will have to make a purchase...