Amazon is offering Photoshop Elements 10 for $63.99 HERE. This is a whole bunch of editing power for a very reasonable price. I highly recommend Elements for novice photographers who are looking to upgrade from Picasa. Photoshop Elements consists of three different editing modes for beginner, intermediate, and advanced users, so it grows with you as you advance in your abilities.
If you are getting into Elements for the first time, visit Adobe TV's learning center for lots of great online tutorials to help get you started.... Adobe TV
I still use Elements 10 coupled with Lightroom 3, it's a very powerful combination.