The 'Portable Hoop Hut' (PDF file) was created by good friends of ours, Bill and Cherie from B&C Kikos and Savanna's, who have now gotten out of the goat business.
This design is easy to build and easy to modify to create smaller versions if needed. The hut is a great Spring, Summer or Fall shelter for your animals.
We have modified the original design a bit to make the replacement of the tarp easier. We now just use 2x4 sections and 'sandwich' the tarp to the landscape timber instead of using the U nails to hold it in place. We also doesn't use the corner braces, and we only use 2 T-posts to hold in place (It WILL become a kite if not secured) but we put one T-post at one corner and the other at the opposite corner on other side. Its a great design and very handy.