With Picasa you can import a picture, straighten it, color correct it, crop it and resize it in under a minute. Here I'll run though these main processes, but there are still more tricks to play with if you want to check it out.
Step 1: Download Picasa
Upon installation, Picasa will catalog all of the images on your hard drive. You can take some time to organize and rename these folders if you want. It's a fun way to kill an afternoon, but let's move on to the processes we're after.
Step 2: Import a Picture
Here, I shot a photo of my right hand to use as an example. The goal is to mimic the Instuctables hand icon. But the hand isn't straight so the first thing to do is...
Step 3: Staighten the Image
My hand had a big angle so I had to do this twice.
Step 4: Get Lucky!
Step 7: Cropping
Here is an example of a 4x6 ratio.
Step 8: Square Cropping
Step 9: Exporting
Exporting in the individual image view will just export that one image. In the library view you can export groups of images from a folder.
In the option menu that pops up you can choose to export at the original size or shrink it down to other preset sizes such as 640, 800, or 1024. These sizes apply to the longer side of the image.
You can also select image quality.