Ask HN: Your best marketing idea that has helped spread the word about your product?

Paul Buchheit at Startup School '08:

Focus on making 100 people happy, and then you'll be validated for opening up your app to more people.

I don't think it's that difficult getting 100 people (especially if you offer private beta invites to smaller niche sites that you're targeting). Plus it gives you a chance to understand what your customers want, which is crucial to early development in an application. You'll need to constantly get customer feedback and validation.

With any product I've worked on that has succeeded, nothing has ever beat word of mouth by way of providing a superior product.

With the software I work on now, every sale we've ever made has been from word of mouth.

Also; I missed you at Gangplank on Wednesday - I hear you don't make it down there much?

Competitions.

Prize can often be trivial/small, but competitions that are fun and involve the userbase often get great response in my experience.

Great feedback everyone, thank you.

Networking.