Apple Aperture 3 ($79.99 from Apple), if you own a Mac, or Adobe Lightroom 4 ($119.31 from Amazon) if you own a PC. These are primarily advanced image management programs that allow you to manage a large libraries of photos. They also have fairly powerful retouching tools, so with them you won't have to spend very much time in dedicated photo editing programs. Both Aperture and Lightroom are fully compatible with external photo editors such as Photoshop, Photoshop Elements, GIMP, etc.

I use Aperture for virtually all image selection, white balance and color correction, noise reduction, sharpening, and light retouching. Only if a photo requires more than a little clone stamping, building composts, etc. do I ever open a dedicated photo editing program.

I believe Photoshop Elements 11 ($71.37 from Amazon) is king among the low cost photo editing software. There's surprisingly little that you can do with the full version of Photoshop that you can't do with Elements. Elements is perfect for someone on a budget or someone just dipping their toe in the deep end of the pool.

Alternative to Elements, if you are a techie and a masochist, you might want to use GIMP (GNU Image Manipulation Program) a try. GIMP (which is free) is powerful, rivaling full Photoshop in capability, although about a generation behind in features. It is an Open Source project and the interface sucks despite recent improvements. (Regarding interfaces of photo editing software: Apple = good, Adobe Photoshop and Elements = middling to crap, GIMP = really bad.)

Aperture + Elements: $151.36
Lightroom + Elements: $190.68