For those of you who are looking for a less expensive alternative to Lightroom, LightZone is an amazing open source application that will let you do some incredible and powerful image manipulation that is sure to impress.
The software was originally developed as commercial software by the now-defunct Light Crafts. Its main purpose is to handle the workflow when handling images in various RAW formats. It is comparable in functionality to Adobe's Photoshop Lightroom.
YouTube videos on using LightZone