Sheldon Brown's Bicycle Technical Info
I really wish they would give up the ads and ask the community for support, I find it difficult to believe that they could not find funding for the site with all the various organizations out there in the bike community who just throw money at such things. A few years ago I could not take the ads on the site any longer and had to enable the ad block, quick look at a random page on the site (canti brake geometry) and ad block reports 30 ads blocked, a little ridiculous. I would pay for an ad free option. Perhaps they will start seeking alternative means now that Harris has closed down. Fantastic site and an invaluable resource to me over the years.