I cancelled my gym membership. Now I just do 3 sets of:
- 1m30s plank
- 20 situps
- 5 leg lifts
- 15 pushups
I try to add a few reps to the sets every week or two and another exercise was a recent innovation. I started out at:
- 1 minute plank
- 15 situps
- 10 pushups
In addition I walk 35-40 minutes to and from work every day.
I know it's not perfect, but to me this routine has really helped! Good luck.