I lift weights several times a week too, for about 30-40 minutes per session. I've got a bench and a squat rack at home, in addition to about 200kg in plates, so I don't feel the need to go to the gym. I just do basic compound exercises, nothing fancy, lifting heavy for lowish reps. I do it because I enjoy it and for variety, rather than to assist with cycling.
It is good to help with weight loss, if that's what your goal is - muscle is more metabolically active than fat, so you're burning more calories even at rest. Also I believe it enhances bone density and helps avoid osteoporosis.
On mondays I do chest exercises - bench pressing mainly. Wednesdays I concentrate on the back - deadlifts, rows. Friday I do a quick session for shoulders - some overhead presses, upright rows, shrugs. And on saturdays it's legs - squats, hamstring exercises. At the moment I do 3 sets of 10 reps for each exercise, but occasionally change this when I feel things are getting stagnant.