Popeye,
I will let Hijort advise you on the business schools. I am no expert in that
As for the essays, I have been through what you are going through. The key, although sounds cliche, is distinguishing yourself. For example, I am a management consultant. The general idea people have about management consultants is good problem solvers and not much managerial exp. So I had to talk about my managerial exp. In your case, if you are a software developer, talk about the business implications of your software, put in it simple words that anyone can understand.
The greatest help for me was the book "How to get into Top business programs" Richard Montauk. It is a great starting point. I would look at all the essays required from the schools you are applying to and choose one school which touches on most of the subjects. For example, I applied to Kellogg, Chicago and NYU. Chicago essays touched on most of the subjects. So I started with Chicago. Once I was done with that, it was about 30-40% more work for the other schools.
Good luck. Initially writing essays can be boring, but later I realized it is the best part of the application process.