Are you looking for complimentay exercises to strengthen yourself for cycling while on the bike? or on seperate days?
As a cyclist you would like to have a stable core and strong lower back. That goes without saying that you need to have shoulders to support your upper body while cycling.
Here are few exercises I would do to help myself become stronger on the bike.
1- Prone iso-abs (plank) with toe lift
2- Side lying bridge
3- Back extensions (with or w/o weight)
4- Single leg squats
5- Reverse lunges
Good luck, and stay strong!