You don't have to do it all in one long session.
One thing I do is 15 crunches before I get out of bed in the morning. It takes 1 minute to do (4 secs each), and doesn't sound like much, but after 2 months I can definitely tell a difference. If you can fit in a minute or two in the morning, maybe do some crunches and pushups or jumping jacks first thing, then go on and get ready for work.
At work take the first half of your lunch break to walk, then the second half to eat, or you can walk on your breaks. If you have the option, take the stairs instead of the elevator, park a little further away from the office, or just any small changes you can make like that. Another idea would be to take one of those aerobic steps to your office, and do that if you get a spare minute or two.
At home, think about getting a stationary bike, treadmill or similar machine, so you can do that while watching tv or reading in the evenings.
You'll find ways to fit it in. Good luck, and welcome to 3FC!