I just recently started using Lightroom 2 to process pictures and since starting to use it I have been sorting by date (starting with a folder for the year, a month subfolder and then a subfolder for that days shots) by backing up to an EHD with the original RAW files. I then import into Lightroom and process those I want to keep and also backup the keepers into a separate folder (That folder is titled "processed photos" and is broken down by subject) on the external drive. I also back up to dvd the RAW files I consider keepers. I label the dvds by the month the pics on it were shot. I also numerically number the dvds as I fill them so they are easy to keep in order.