Some general advice I'd provide is:
- Figure out the characteristics of your users. What kinds of people have the problem you're solving? Be as specific as possible, and segment into multiple groups. Think about age, gender, interests, activities, group memberships, places.
- What kind of tools and services do those people already use? How do those services get their users?
- Where can your different types of users already be found? What communities are they part of? What types of sites do they frequent? http://quantcast.com is a great tool for this. This list: http://socialmediaanswers.com/niche-social-networking-sites/ and lists like it are another good one.
- What kind of things do your potential users talk about? Can you find them using http://search.twitter.com and http://blogsearch.google.com/blogsearch ?
Good luck!
You don't approach the problem backwards, that's how.
A "product" without a need is like an answer without a question. You should always have, at minimum, at least 1 user that finds the product useful before you even develop anything.
Assuming you have a least one person who is having a problem solved by your product, the issue then becomes to find other people with the same problem. Your product should sell itself to them.
What problem does your service solve?
Who has that problem?
Go introduce your problem to them. If this model doesn't fit for whatever "but, but" you can come up with, I would humbly suggest abandoning this product and focusing on another.
It is a tool oriented toward programmers and from what people have been saying it seems like you just have to get it out there and also combine it with a little advertising for things programmers might search for.
Either Organic (SEO), Social media (Twitter, Facebook, Blog posts) or PPC (AdWords, Ads on relevant blogs).
If your service is truly unique you might find some good rates on keywords.
Link I'm referring to so the original commenter doesn't have to re-edit: http://www.gabrielweinberg.com/blog/2010/04/ways-to-get-100-...
-join niche forums and participate