Learning to PP

I found Mark Galer's book Adobe Photoshop Elements 10: Maximum Performance very helpful because it was good blend of understanding the technology and showing what could be done with a range of pictures.

I think it is easier to learn using a good tool. Picasa isn't bad, especially for a free program, but it is quite limited in some ways. It's well worth investing in Lightroom or Photoshop Elements. Lightroom is a good starting point because it is very capable yet doesn't have too many features to learn.