Horse Shade is always a big concern for us, we usually have at least 10 horses at our ranch.
A good solid freestanding aluminum awning makes a nice horse shade. Below you will find the best on the net in the way of plans, products and books about horse shade.
Tarps can be a great start for an inexpensive horse shade. Visit this page for some tarps and ideas for their many uses. Tarps can be attached to any type of structure you may have. Build a simple 2 x 4 frame and staple or bungee the tarp into place and you have a nice horse shelter that won't cost you an arm and a leg.
Below are a few examples of horse shelters and how-to books.
VersaTube Steel Shelter (#ad)
This is a book about how to build an all-purpose 30' x 24' barn with site plans. It also includes how to adapt this basic barn for use as a garage, carpenter's shop, artist's studio, apartment, or garden/animal shed.
Below are a couple of inexpensive horse shade ideas by ShelterLogic.
ShelterLogic (#ad)