I could answer this a million ways, even suggest some bike models... but here's my best answer:
Visit your local bike shop,
explain what you want to do with that bike
and what your target budget is.
They will set you up with a properly sized bike, spec'd to fit your budget. Or use their recommendations to help you shop in the used bikes classifieds.
Avoid stores like costco, wal-mart and other places where the bikes sit there, next to BBQ's and cat food. They can't fit you properly!