Matt Magain has a great April Fools article on how you can build a wildly successful Web 2.0 application without ever actually writing an application.
Publish an API for your application to get developers interested in hooking into it. Implementation of specific methods isn’t important at this stage; just put a series of stub methods in place that return the value 42. Don’t worry, they’re geeks — they’ll have read Douglas Adams, so they’ll get the joke. Not only will they forgive you, they’ll like you even more for your subtle humour. And if anyone complains, remind them that your app is still in beta.
As the (oft-quoted) saying goes:
0: Create a catchy name.
2: Sell to Yahoo.