I get most of my exercise from walking (and hiking, paddling, that sort of thing) - but I've been trying to get in a little movement to raise my heart rate, too. I found this 15 minute aerobics video that is fast, fun, and easy - I find it very easy to just do it in the morning as I am getting into my day (I work from home, which makes this easy) without it disrupting too much. This guy - Body Project - has a bunch of others as well. I like the 30 minute video when I have more time and am not walking as much, and I'm sure he has others that I would like, too, if I get around to trying them.
I will invite the naysayers to keep quiet about how that's not enough exercise, not enough cardio, etc. For me, now, it's good (on top of walking for almost two hours a day, but even if not - this makes exercise very accessible).
Anyway, I thought others might find this good, too - so:
And now: Do you have any fast-ish workout videos you like, for when I get tired of doing this one?