Here are some thoughts from someone that finished a masters in computer science four years ago.

My experience at the University of Colorado at Boulder was wonderful. The classes were top notch and my committee was both supportive and friendly, so I'd recommend that college highly.

Choosing a college and area of emphysis is tough. After choosing U of C at Boulder, I interviewed professors to see what they liked researching, if they would accept students, and if our personalities matched well enough. Reading papers published by the professors first provided a place to start asking questions. Don't let the research area control your choice, as I believe that part about personalities matching well is critical for success. At the same time, if your research is in something you find fascinating the work can actually be fun. As with life, it's all in finding a balance.

Looking at industry and employment trends can be helpful. My current employer generally won't look at developers without a masters degree, but we're a bioinformatics research group. For bioinformatics, they seem to look for a masters along with experience or degree in biology, math, or another life science. Data mining seems to be a growing area within bioinformatics.

I'd agree about GIS being a growing area. A masters with a specialty in statistics also sounds interesting, as many industries then need your skills.

Good luck and don't forget to enjoy the ride,

Bryan