Two of the best people who are not selling anything are Tom Anhalt (http://bikeblather.blogspot.com/) and Robert Chung. They both post a lot in various forums like Weight Weenies (which is more about rolling resistance and aerodynamics now that we know that they are more important) and Slowtwitch (more triathlon focused but has a lot about general bike tech).

Josh Poertner from Silca is also good but has things to sell.

Of course what everyone is saying above is right -- fitness and rider weight matters the most. But it is fun to look at this stuff especially once you have achieved some level of fitness.

I don't know but I'm also not trying to market very expensive tyres.

bicyclerollingresistance.com