It’s not like you couldn’t see this coming. After all, Jeremy Zawodny was asking about Yahoo APIs back in September (even though he claimed it wasn’t in the works and maybe wasn’t yet). But tonight Yahoo! made it official and launched the YSDN.
You can find all the fun at developer.yahoo.net.
UPDATE: Here’s an excellent example Yahoo API implementation from Paul Bausch {via Waxy}
{via Battelle}