Workout for the Office

I recently started getting my weight back on track. I have found a diet that is working for me and something I can see myself staying on when I finally get the weight off. I recently bought a treadmill and I have been trying to use it at least 5 days a week while watching my shows in the evening. I have recently started to incorporate a strength training into my day. My problem is that I sit at a desk all day. I notice on the days I get up and do squats, push ups, ect. that I feel better and want to work out in the evenings. My question is does anyone have an other body weight exercise that can be done in the office. My day is sometimes super slow and then other days it keeps me pretty busy. My boss are pretty laid back as long as my work is done they don't care what I do with my free time. Today I brought in a 12 in step and did some steps but found my self pretty winded when I went to answer the phone. An extra small work outs that are possible to do in an office would be wonderful.

Thanks in advance.