I found this tool a little while ago and thought I'd share. If you don't have a photo editor like Photoshop or The GIMP, you can use this site to do some common things with your image.
You can shrink your image to an indicated pixel size, add greyscale or sepia effects, and even choose the image quality. Plus they have a special avatar tool which not only resizes the picture for you to a proper avatar size, but will do different cropping samples as well. Then all you have to do is grab the image and you're good to go.
What I love about this tool is that the functionality that it offers is about the only functionality that I use for images anyways, so it's very handy. And because it's online, you can use it anywhere and load it up to your image server. I've always had a server to load the image to, but I didn't always have a tool for resizing. It's easy to use, and you don't have to install yet another application where you only use about 1% of the functionality. Good times.
Original picture (click picture to see original size, Blogger is resizing pic):
Cropped to 350 px height (click picture to see new size):