Our API directory now includes 71 url-shortener APIs. The newest is the Proofeditors.com API. The most popular, in terms of mashups, is the Bit.ly API. We list 32 Bit.ly mashups. Below you'll find some more stats from the directory, including the entire list of url-shortener APIs.
In terms of the technical details, REST and JSON lead the way. There are 56 url-shortener REST APIs and 3 url-shortener GET APIs. Our directory lists 41 url-shortener JSON APIs and 30 url-shortener XML APIs.
Tiny-URL Open API: URL shortening tool