I decided not to drop this in Project Development as it's not just specific to Bitcoin.
I've been working on a 'development collective' for a while now (
http://www.cryto.net/) and by now there is a fairly solid not-quite-a-CDN running. Right now it's essentially a redundant Tahoe-LAFS storage grid with 5 geographically distributed "gateways" - it's essentially a bit like a CDN without the geotargeting. GeoDNS *is* planned for the future, but right now we don't run our own DNS servers yet.
What it does: it delivers files. Any and every kind of files. You can essentially upload a file to the storage grid, and get back a 'read URI' that can be translated to a 'gateway URL' - which is essentially just a URL that anyone can access to download your file. It provides provider-independent security (meaning that you don't have to trust a third party to use it) as the only way to read a file, is using the read URI - which is also a decryption key. While using the standard gateways you have to trust the gateway provider (which right now is pretty much me) to not intercept your data, you can easily set up your own gateway.
There's about 500GB of free space across the grid right now, which should translate into about 200GB of usable space with default settings. Usually any 4 servers can disappear from the grid (which right now consists of 10 servers) and your files should still be retrievable - if you change your settings you can even make the reliability higher.
Now what am I offering? Basically free (unlimited, within reason) usage of that not-quite-a-CDN for non-profit projects. Tahoe-LAFS relies on Python and Twisted, and provides a web API, so it should be easy to implement it into your application. An I2P tunnel for the main gateway is available on
http://cryto-gateway.i2p/, while the clearnet gateway runs at
http://tahoe-gateway.cryto.net:3719/ (links are interchangeable across gateways, so you can just change the gateway address to make gateway links work on I2P).
An example snippet of PHP code that I am using in the new version of AnonNews to store uploaded images on that grid:
$tahoe_server = "http://localhost:3456";
$tahoe_gateway = "http://tahoe-gateway.cryto.net:3719";
$upload_result = curl_put("{$tahoe_server}/uri", $_FILES['file']['tmp_name']);
if($upload_result !== false)
{
$upload_b64 = urlsafe_b64encode($upload_result);
$upload_url = "{$tahoe_gateway}/download/{$upload_b64}/{$_FILES['file']['name']}";
}
... where $upload_url is the public HTTP gateway location of the file - anyone can go to that URL (or for example set it as img src) and see the uploaded file.
If you're working on a non-profit project that could use redundant file storage,
hop on to the Cryto IRC and let me know
Of course donating server space or even running a gateway (small 1-file Python script) is also welcomed very much.
EDIT: A quick diagram I made of the current grid setup (minus the 'tahoe-lafs clients' that actually upload data, this is just the delivery part):
http://tahoe-gateway.cryto.net:3719/download/VVJJOkNISzp1eHJyc3huemo3ZzYzdmR0N3E3cGY2bzd1aTp2ZG5oa2d3eTV3cmxjcHlvb3B3ZmFzb3duNjRoMmFkNm4zZ3dnZHppenV3ZXJpdnc3bDNhOjM6NjoyODk0NjA=/cryto-tahoe.png 
