I have not found very many resources for field courses. I am making videos for the field sites for aquatic ecology, and stopping to ask questions throughout for different methods (iron, flow, riparian zone management). I will also collect macroinvertebrates and take photos and then have students identify and count. I will also making videos for some of the test kits.
I added a citizen science component to the class as well so students can collect their own data in their backgrounds. I am using Budburst but scistarter.org has tons of projects both online and for the background.