The eBay Ruby library by JJ Buckley interacts with the eBay Trading API, that works with items, listing, and users. To use the eBay trading API, a developer key is needed. The keys will be used starting with the access to Ebayr, followed by generating a RUName using the Ruby gem.
Looking through our directory of travel APIs and getting lost? That's no surprise; we've cataloged 168 of them so far. Fortunately, Valentin Dombrovsky, CEO of Travelatus did a great service by focusing on the 5 he says, "are the ones that offer interesting opportunities for your site—no matter who you are, an OTA, an airline or a hotel chain, for example." Writing for Tnooz, the magazine that talks travel tech, his 5 picks are rome2rio, DealAngel, Evature, Flightstats, and InKnowledge's Taxi Fare Calculator.
Wolfram Alpha, the up-and-coming "answer engine" that we reported on back in May, has just released an API that developers have been awaiting since this spring. The new RESTful API provides access to the vast stores of data and computational knowledge available through the Wolfram Alpha project (technical details at our Wolfram Alpha API profile).