This article has some big picture ideas for learning outside a classroom; my favorite is the fourth section down: Technology Outside the Classroom. I never thought of how students could use their own technology within nature to learn!
I think logistics can be the trickiest part sometimes! Check out these fun ideas for places to sit. For inner-city schools with limited space, I love the large buckets idea. Follow this link back to the home page for more ideas!
Schools with "hands-on environmental curriculum" had a 100% improvement on student behavior?!?!? I might take my students outside everyday! Check out this article for more on that finding and why we can all benefit from getting our kids outside (and some tips on how to do it).
This could be a powerful way to start getting students primed to be observers of the outdoors. Nature holds many powerful lessons...and if it's doing the teaching then you can finally finish your cup of coffee!