Henk Van Ess has revealed, via his SearchBistro site, Google's "secret" lab - online at https://eval.google.com that lets users recruited by Google as search testers to rate and analyze search results to help select the best algorithm.

A video at the post shows how the very low-tech system operates and returns results for the Google engineers to pour over. It's basically a simplistic comparison system that lets the users select which of the 2 top 10 results is more relevant.

This is also a great way to filter spam from the top pages of common queries, as Google clearly has staff reviewing websites manually and knows what their most common queries are. Whether this phenomenon has anything to do with the sandbox or not is debatable, and it has been revealed previously at several of the forums via job postings. But, this is the best insider look to date at the process of manual reviews at Google.