eBay4R is a Ruby wrapper for eBay's Web Services SOAP API. Has ease of use and small footprint. Instead of 40-50 line examples eBay gives you in C# and Java, with Ruby and eBay4R, examples are 5 lines or less.
BIPS, Bitcoin payment system, allows users to buy or sell online using Bitcoin digital currency. In addition to Bitcoin transaction-based apps and an e-wallet, BIPS provides an API that users can integrate with existing workflows and tools. Merchants can utilize Bitcoin currency alongside traditional currency transactions.