Motivation? What's that?
I made exercise a must-do. I stuck it in during a no-excuses part of my day, which for me is 5:00 in the morning.

It's not so bad now that I'm used to it. Shoot, I try to sleep in now and can't get past 6:30!
In addition, I also created a baseline of must-do activity. I chose something that was easy and sustainable. For me that's spin class M/W/F and lifting T/Th. When I don't feel like exercising, I do that as a bare minimum. Exercise doesn't have to be hard each and every time you do it. I think it's more important to do something...anything...for a period of time especially when you don't feel like it, just to keep the routine. Otherwise it's way too easy to start making excuses. There's no room in my method for excuses. I don't talk myself out of brushing my teeth in the morning and I don't talk myself out of exercise.
But as for motivation, I find people very motivating. Right now my gym is having a little competition to increase our cardio. Several of us put money in a pot and we're each collecting units for every 15 minutes of cardio we do per day. The person with the most units at the end wins the pot. Let me tell you, I am highly motivated at the moment!

Perhaps you could organize something like that with some friends.