Another temporary option for the colder months of the year is to use curtain clips to hang a thick insulation behind summery curtains.
Command Hooks To Hang Curtains: No drilling required. This is a quick and easy way to add a little class or keep extra light out.
Great idea for window treatments for apartment dwellers -- really could have used this in college
Crochet curtain of Japanese Flowers by BautaWitch and Findus Zlatan, the cat. <3
http://www.phomz.com/category/Valance/ DIY No Sew Valance Tutorial More
DIY project. Imagine doing one of these and hanging instead of curtains.
Google Image Result for http://1.bp.blogspot.com/-TgO7C42NocM/ToUXZyqpJnI/AAAAAAAATBw/mDbKbhDCHlM/s640/DSC_0993.JPG
Bermuda Shutter Hinge Pair
A personal favorite from my Etsy shop https://www.etsy.com/listing/477882570/boheme-gypsy-love-struck-curtains
Would love to do something like this to the windows in the kids' rooms. From: ScrapRoom Makeover (on a B.U.D.G.E.T) - Two Peas in a Bucket