Geocaching and GPS are important parts of today's nature-based field trips. This is a useful website for this. Of course, now many of us are using smart phones for this capability and many of these links need to be updated to reflect this, however, I believe we're going to see some very interesting gps-enabled field trip and documentation tools for this.
Free textbooks in a variety of topics on CK-12. This is promoted as "learning made simple." Do students know how to find and download alternate sources of information? Can they find and search for the topics they are currently studying? This is a valuable way to compare and research topics.
HOw to borrow Kindle books from your local library. It often requires setup of overdrive here in the US. This is an important skills for modern students, particularly if they have a tablet device, they should know how to check out books from their local library. Don't show them how to use the card catalog, set them up on overdrive and show them how to use it.