I know by now it's a bit "old school" but I used to do those walking dvd's and sometimes still when I'm cooped up cause of the weather, I'll jump up and walk my way through the commercials. I also do that when I can't find the remote to change the channel during commericals.

A not so "fun" (at least not to me, it kicks my butt) but good move that I also do indoors is to do squats with your arms in 3 positions for 8 counts each- pointing down behind you, out straight to your sides, and up over your head. You end up doing it 40 times (also have to do it with arms on way back down). My dance teacher has us do this to warm up and she got it from someone who went to one of those women's boot camps.

Tae Bo (there's apps for that to start) - I don't know about the fun factor in that, but I'll try it.

As mentioned in another thread, I'm doing Tae Bo with the weighted gloves. I love the boxing elements (as I boxed until I was out of college and loved it), but dang this thing is kicking my butt. Monday I got through 10 minutes. Wednesday through 15 minutes. About to do my Friday workout and hoping to push a little further. It makes my arms feel like they're going to fall off, but I definitely want to do some toning while I lose so I think the weighted gloves are important.