Keyword search tool or API

[webindustry]

Anyone have a suggestion for a simplistic (scaled down) version of a keyword research tool that I can put on our website? We need our clients to be able to perform some basic keyword research on their own without getting lost in the details of something too robust.

We would like to control aspects of the tool, capture the data from the site visitor and move those results (from their searches) into a database or other web application.