Vik over at The Lazy Randonneur occasionally posts "bike porn" - salacious pictures of beautiful bikes for people who have a real affection for such things. Here I will post some "greenhouse porn".
Doug Leen lives in Petersburg, Alaska. His greenhouse (pictured above) is simple and beautiful. Essentially it looks like a modern trestle frame or truss frame design. I'd like to build one very similar. One thing I might add is eye bolts and cables for diagonal bracing along the walls, but rigid polycarbonate panels serve the same function.
Rosie Creek Farm has a beautiful collection of greenhouses used to grow their organic produce. One might say this is simply a larger version of Doug's truss frame greenhouse (though it was built earlier, another view). The larger roof span benefits from a more triangulated truss design.