Sell hosted content online. Two simple pricing structures 5.9% plus 95c per transaction or 8.9% with a 75c per transaction minimum. Highly customised order pages.
Official list of Ubuntu mirrors including very useful information on how up to date they are and their available bandwidth.
Simple site to sell downloadable content. Integrates with a few payment gateways, PayPal, google checkout, amazon payments, and probably others. Free up to $50 a month or 5% plus 49c (5c < $2) per transaction, in addition to any checkout fees I assume.
The Ubuntu package list. One can find .debs to download here.