Google App Engine as a CDN
If you are looking to offloading some of your bandwidth costs to the great google, and were thinking of using the google app engine as a free content delivery network, then have a look at the cirrux cache project.
Installing it is pretty straightforward, considering you follow the quick installation guide as stated in the readme. If you are looking to use this along with your wordpress installation, then have a look at this link, which gives a much better and easier explanation and a step by step approach on what you really need in order to set up.
Using this technique may also help because the HTTP/1.1 specification suggests that browsers download no more than two components in parallel per hostname. If you serve your images from multiple hostnames, you can get more than two downloads to occur in parallel.
If you are feeling lazy and just want to use something, then have a look at http://cdn-cloud.appspot.com/.