DHTML/AJAX experts: Type-ahead SELECT dropdown

This project’s aim is to develop a type-ahead selection box with to draw data from my database. Focus on small script size is a must, having to include large size libraries is NOT acceptable! Requirements: Type/Select a state in dropdown box -> New Select/Type city box opens beneath Type/Select a city in dropdown box -> New Select/Type community box opens beneath Type/Select a community in dropdown box -> One of two things can happen: 1. Community which is currently in database will populate a page with that community's information OR 2. A simple form will pop-up allowing for the addition of that community to the database by a registered user. So, the three boxes draw on data from the database. If the Community is not in the database already, registered users will have the opportunity to create it by filling in a simple form with to include: a. Name of the community b. Zip code. c. Comment on the community (optional). PS. The comments need to be tied in with Jom Comment component.