Depending on your situation, incorporating active transportation into your life can be extremely efficient. When I started biking it took me 15 min to drive, park, and walk to my office. It took me 20 min to bike. Round trip is 30 vs. 40 min-- only 10 minutes of my day and I get a 40 min workout.
If you live too far, replace part (not all) of your commute with biking, leave your car at a church or business (ask permission).
Or drive to work, leave the car at home and bike home, bike to work the next day, drive home with the bike.
Or if you have other constraints, people get really creative to make it work.
You can get a surprising amount of exercise by always taking the stairs-- even to the 7th floor, parking in the farthest corner, using a bathroom that is further away or on another floor.
As others have mentioned it depends on your goals. All of my solutions work if your goal is to be healthy, they don't provide for specific training to make you faster.
2009 Trek 7.2FX WSD, brooks Champion Flyer S, commuter bike