Use a jar to create a humid cave for your hermit crabs! #DIY- PetDIYs.com
Sand caves. Instant shelter for your hermit crabs. Use a clean, cut top half of a plastic bottle, burrow horizontally into a heap of moist sand to create a sand cave for your hermies, they will love it.
Create an extra-humid area for your hermit crab! DIY Log Humidity Hide - PetDIYs.com
Mini planters filled with moss and coconut fiber. I pour water on them daily to keep up humidity. Good for the crabs to climb on too! Attached them to a plastic cake dowel wrapped in plastic canvas using plastic string since they each have a hole in the bottom.
Provide deep pools for your hermit crabs. You may not see them, but they do completely submerge sometimes.
These are hermit crab pools. This isn't a DIY, but this article can give you some ideas. It is beautiful. I am going to be making a DIY for hermit crab pools soon on my blog, http://careforyourhermiebabies.blogspot.com/ but my crabitat is not yet ready for the pools. Hopefully it will be posted up on my blog by July 30th.
DIY Hermit Crab Jungle Gym - PetDIYs.com
Take an old end table and turn it into a Hermit Crab home!