Ask Jeeves/Teoma
Google
Mooter
1.American Philatelic Society  Coin and Stamp Collecting (About.com)  Stamp Link-Philately, Stamp Collecting’s Best Site in Its Category
2.Joseph Luft’s Philatelic Resources on the Web
Joseph Luft’s Philatelic Resources on the Web
Warragul Philatelic Society (Stamp Collecting) 
3.Linns.com: The website of the world’s largest weekly stamp newspaper-Linn’s Stamp NewsAmerican Philatelic Society Postal history, philatelic covers and stamps for sale
4.Stamp Link-Philately, Stamp Collecting’s Best Site in Its Category BNAPS Stamp Collecting for KidsGreat Britain Philatelic Society
5.Philatelic.Com Linns.com: The website of the world’s largest weekly stamp newspaper-Linn’s Stamp NewsStamp Collecting, Philately, Stamp Auction
 The top-ranked page has the highest “authority” -essentially, the most links-among communities of Web sites about stamp collecting. It’s validated by references from resource pages (link collections from experts and enthusiasts-in this case, stamp collectors) and link popularity measurements similar to Google’s. The runner-up, Joseph Luft’s Philatelic Resources, has fewer and less qualified referrals from experts on the subject. Google officials won’t discuss how the Google engine arrives at rankings for specific sites. Patent documents and published papers, however, show that Google ranks pages according to how often other pages link to them. Google also takes into account such factors as the relevance of the referring pages and the text surrounding the links. Presumably, collectstamps. about.com is the most cited page on this subject in Google’s index.Mooter first groups results into clusters or themes. The pages shown above appear in the “philatelic” cluster, ranked according to how frequently the search keywords and the cluster name appear on each page, among other factors. Mooter “learns” the user’s intent by noting which clusters and pages are clicked on, and reranks the results to reflect the apparent pattern of interest.