My advice is to start small and build your way up. Just ten or five minutes a day can still count.
I highly recommend the website Spark People TV for lots of free workouts. Chair exercises are also a really good option.
I also recommend bubble jet spa foot baths. I had a job before where I was constantly on my feet and always tired. Soaking my feet at the end of the day was something that really helped me relax and energized me at the same time. Plus, they are going down in price. They have them at places like Walmart and Target but I will leave a link for that too.
Hope these help!
Chair Workout:
http://www.sparkpeople.tv/video.asp?id=633
Bubble jet baths:
http://www.homedics.com/spa/footbaths.html