I've just finished an online service for shortening URLs (in php5 with Zend Framework); you can enter an URL and you get an short URL (like tinyurl and such sites).
I'm thinking about the API for developers - at the moment you can send URLs with SOAP to the service, but I am not sure if this is a good solution. What is the best practice for such a service? REST? SOAP? Both?
Definitely REST - the overhead for SOAP is unnecessary unless you're building a particularly secure enterprise URL shortening service (which I think is probably an oxymoron). The bit.ly API is pretty good and worth checking out.