1. Create a simple prototype that demonstrates the core ideas of the concept and show it to a few people (you trust). You may be able to attract some good developers if it appeals to them.
2. Start a blog and talk about how your idea may benefit some potential customers. See whether any one shows interest.
3. Go to one of the startup meet ups (www.meetup.com) in your area and informally discuss it or present it to the group.
4. You may not need to build the entire software. Most of the good developers know how to reuse existing software (libraries) to quickly build a version 1 of the product.
5. Try a few interns from your local computer school and let them build the first version of the product. Let a few friends try it out. If there is enough interest, you may be able to find some supporters in funding it or developers interested in developing it further.
6. You can start a project in one of the open source communities like sourceforge put some high level specs and see whether any one will be interested in joining you.
7. If you strongly believe in the idea and do not want to go open source, prepare a simple plan and approach some angels. Many angel investors may also have a good rolodex of development resources.
I think having a good idea for a great app is cool. But you need to go to the next step of prototyping or let others visualize it so that you can get some reactions. This will help improve the idea and also hear if such an idea is already implemented somewhere else.