When we use to work on the Google Search Appliance, one of the most difficult issues was getting the crawler through the web form. It was a black art that I perfected and wrote about. (you’ll have to goto the internet way back machine to look that up)
Ultimately, Google provide this feature after they wound down the product. Wait no more…Coveo has added it as well!
When creating a Web or Sitemap source, you now have two form authentication options: Manual form authentication and Automatic form authentication. While the Manual form authentication option requires you to provide the form input names and values, the Automatic form authentication option detects these inputs automatically.