Picasa is a free photo editor from Google. It includes features to organize your photos into albums, and some great simple image editing features.
(Click logo to go to the Google/Picasa site.)

Basic Fixes are back – and better.
Picasa's Basic Fixes are buttons that make it fast and easy to crop, remove
red eye, fix the contrast and color, and enhance your digital pictures.
Amazing effects turn so-so pictures into works of art.
You can see how much Picasa's 12 new visual effects can improve your photos – and
in seconds, not hours. Go sepia. Warmify. Make pictures pop with color or
try austere black-and-white. Try easy one-clicks or the more finely tuned sliders
for better control where you want it. And of course, you can undo your changes
at any step along the way.
Write captions that stay with the picture.
Picasa makes captions the way journalists do – using the IPTC standard.
That means your captions are saved within their pictures and stay with them,
whether you export as a web page or make a CD presentation. Picasa captions
are fully editable and searchable, and you choose whether to display them or
not.
Zoom. Pan. Tilt. Get the angle you intended.
So you did not get the shot? With Picasa, that is not the end of the story.
Go in closer and move the focus slightly to the left. Your camera was slightly
crooked? So what? Your picture is perfect anyway.
Know how to use a camera in manual mode?
Photography aficionados can now fine-tune their photos with Picasa's EXIF
display. This window shows you all the camera data that is stored in a picture's
original file - such as camera model, date the photo was taken, even if a flash
was used. The EXIF display also has a RGB histogram, a real-time graph that
shows the intensity of colors in your picture and how they change when you
make edits in Picasa.