Google announced that Googlebot will be able to crawl the drop-downs and html forms of various websites. Initially there were issues in detecting the content/pages behind the forms and drop-downs. We had the same issue with one of our client and now I am sure we can find the googlebot crawling the form pages and we can then add that in our future client recommendations. Matt Cutts has provided some good analysis on the topic.
http://www.mattcutts.com/blog/solved-another-common-site-review-problem/