Cycling will tone all of the muscles in your legs. Climbing hills will target the hamstring and gluts more. You want to keep your cadence around 70-90 rpm's with a lite pressure on the pedals. That will use you slow twitch muscles that can go for a very long time.
To target the hamstrings more use more pedal pressure like climbing hills or use a higher gear. Reverse leg curls will target those muscles.
http://www.google.com/search?hl=en&q=reverse+leg+curl&aq=0&oq=reverse+leg&aqi=g10
