Like the subject implies, I've got nothing against exercise but the very last place I want to do it is in a gym. So I'm willing to invest in exercise equipment when I know I'll use it (and have somewhere to put it!)...
For several years we had a treadmill and then switched to an elliptical trainer for lower impact. Two years ago my herniated disc acted up and made even that a problem, and it's been rarely used since. Now I just try to get outside and walk at least 5-10 miles/week for that kind of exercise.
Fast forward to Sept. 2011 and my PT after (very successful) back surgery. The vast majority focused on core strength, with additional muscles being put to work as the core got stronger. You can probably guess that most of the exercises are straight out of Pilates, and the same for the equipment.
While it'd be cool to have a Reformer and Trapeze and be able to do the full range of Pilates work, I don't have so many thousands of dollars *or* an entire free room. But I've settled on the next best things: a good floor mat ($50) and a Pilates "spring board" ($450). Between the two you can work just about any muscles in your body. And for space all you need is that one spot on the floor for your mat, next to 3 ft. of free wall!
There may be others, but this is the spring board I bought: http://www.pilates.com/BBAPP/V/store/trapeze-tower/pilates-springboard.html
If you do get one, I recommend getting the spring board and mat exercise books that they also sell. In addition to detailed instructions, all the exercises are rated beginner, intermediate or advanced. But if you've never had any
Pilates-based instruction, you should probably try to get to a PT a couple of times to make sure you're not doing anything injurious or counterproductive...