Living in a warm climate I like thinner breathable socks. Paired with breathable cycling shoes (Sidi in my case) my feet feel much cooler when sweating like a pig. You can get them at places that sell sports apparel but they tend to be the short ankle socks so they don't look "pro." I usually end up paying $10/pair for the cycling specific ones. Current favorite is the Giro Classic Racer socks.