I've been based at home for 2 years or so studying and have found that the weight has crept on (well an extra half to one stone) and even with exercise / sensible eating it's hard to lose the weight. I am sure it's done to being sedentary. When i worked in London I walked to tube, walked at lunch time and as a trainer was on my feet all day, pacing the training room :-) I also think that the mental / physcial nerves/ fidgeting also burnt up calories :-) I'm hoping that when I go back to work I'll be able to lose the last half stone or so...
For exercising at home, I definitely recommend Davina's power of 3 DVD. It takes about 1hr 10mins in total, warm up, 3 different sections of 20mins each adn then cool down, so if you're pushed for time you can just do 2 out of the 3 sections. It's a mixture of aerobics and weight exercises, and is hard work, but it's made a big difference to me, and my bingo wings have gone :-) Plus I can now do full press ups, three lots of eight, and even mr.ncot is impressed !