How to do a pre-beta invite promotion
jsean: It's very hard to get people interested without actually having something tangible.
Make sure you produce an alpha version to which you invite a couple of feedback generators.
Friends, family or perhaps a couple of hardcore believers.
Next step is to get a decent beta and make it open.
How open is up to you to decide.
But this is nonetheless the step where people you don't know of actually tries your app.
(be sure to make it easy easy easy to give feedback, generally people find wasting time on noble causes boring)