The other day at SEOmoz Randfish explained the importance of the Google supplemental results query with enough words to fill up ten minutes of your time, but most importantly with clear images that depict in a funny, original manner, the relationship between the Google bot and the pages that land in the supplemental index.
Although Randfish starts from the idea that the supplemental results query on Google doesn’t work anymore (it was probably a temporary problem) the main idea of the article is really valuable for any site owner.
The article teaches you how to identify orphan pages and the reasons for their landing in the supplemental trap.
It also tells you that with a bit of link love your pages will make it out of these supplemental results (which is absolutely true if you do it wisely). Remember: not all links are good links and not all links bear the same value. Especially stay away from paid links.
There are many techniques that will help you improve your pages, and get them out of the supplemental results, some of them already described at Search Engine Oracle. You should not count solely on links. You should optimise your pages completely: better content, proper coding, relevant (and unique) page titles and meta tags, good image attributes and so on.
In the end, I cannot help but partially agree with Randfish’s idea: the information about the supplemental pages should be designated solely for the eyes of the website owners, but the thing is that these pages do appear at the end of the main search results when not enough terms coincide with the searched terms. So even a supplemental page has a chance to be found. Should Google really eliminate them out of the query search?