Note: sorry if any of this is badly formatted, I don't post often
Health is a broad topic and it really comes down to what you're actually trying to achieve, 'staying in shape' is a really broad area (gain lean mass, reduce heart risk, age well, endurance, fast-twitch response, weekend athlete, don't throw my back out doing the lawn, etc), however, here's some general advice on overall directions:
Work can bring you down, and when you're sitting down it can be hard to focus (or the opposite, if you've ever done a 10 hr marathon coding session, looked up and said 'damn'), relax, or keep a stable mental state (depending on your user base) ~ http://www.guidetopsychology.com/autogen.htm
~ is one method of staying focused and giving yourself the reinforcement that will help with the other steps (you can get it down to about 3 minutes front to back by the end of the cycle).
Nutrition: Other than a balanced diet (there's too much info on google to address that here) a good vitamin pack ~ http://antiaging-systems.com/a2z/beyondchelation.htm
~ can go a long way to stabilizing your diet and 'rounding off the rough edges'. I like the chelating package because it helps cleanse some of the crap that gets into the food lifecycle out of our system.
At work exercise: http://www.amazon.com/Isometric-Power-Revolution-Mastering-Lifelong/dp/1932458506
~ is a solid reference on isometric exercises (many of which can be done at work) - optimally spread out throughout your shift (and some can be done discretely on an hourly basis). There are many isometric references out there so if you find this trend working for you then you should continue to do research until you find a series (with variations) that meets your specific (and evolving) needs.
Day off exercise: 2-3 30m cardio sessions are good, but I also recommend 1-2 yoga sessions as well (or in place of perhaps). Yoga is an excellent method of flushing your lymphatic system and has solid health benefits for arterial plasticity as well (make sure you do your own research however), a good at home example guide is: http://www.amazon.com/Bikrams-Beginning-Class-Second-Edtion/dp/1585420204/ref=sr_1_1?ie=UTF8&s=books&qid=1246481279&sr=1-1
You can get the info in the books above on the internet as well, but I like books for my library.
The above require the lowest investment in equipment that I've seen and still allow for considerable improvement and variation. There's no magic pill here, you have to really define what you want to achieve and keep learning to adapt your regime to your lifestyle/goals. Keep in mind there's a difference been an 'optimum' workout strategy and 'making a difference'. Doing 5 minutes of isometrics or a breathing exercise or two every hour at work isn't an optimum way to build muscle, but every little bit helps.
Best of luck