When the big boys run websites they use Content Delivery Networks (CDN) to host most of their content, especially images, stylesheets, files to download and other static content. The most famous CDN is probably Akamai, that almost run their own parallel Internet. Akamai and other CDN providers (Amazon) cost big bucks though, so it is nothing for us mere mortals.
But thanks to Google anyone can now run their own CDN for free on Google servers. It is really easy to set up and storing files for downloads, stylesheets etc on Google instead of on your own site takes the load of your servers.
What is Google App Engine?
Using Google App Engine you can run web applications on Google’s servers. That means that you can benefit from Google’s huge world-wide server farms, it means that it is really easy to scale and to integrate with other Google applications (for example using Google authentication in your applications). The App Engine is Google response to Amazons very successful web services S3 (for storage) and EC2 (for computing). Amazons services are very powerful, but they do require a deeper level of technical knowledge to use than Google App Engine.
Google App Engine is free for anyone to join, all you need is a Google Account. What you get is 500MB of free storage and around 5 million free pageviews a month, if you use more than that there is a small cost (see the Google App Engine blog for more details). The cost for these extra resources are almost the same as for Amazons Web Services, and with the freebies and ease of use thrown in Google App Engine is a bargain.
You can check the statistics of your Google Application at appengine.google.com. For example you can see how much bandwidth and disk space you are using. It will take quite a lot of files and usage for you to use up the resources you get for free, but if you have a super popular site then it is worth taking a look here every now and then.