Martin Houses
Everyone has seen multi-deck martin houses that look like a hotel from the 20th century. Instead of sticking to the norm, build several dozen gourd houses for the martins. Building birdhouses out of gourds is a long-term project unless you buy a gourd that is already dried. Start by planting birdhouse gourds in your garden and grow them over the summer. At the end of the year, harvest your gourds and allow them to dry over the winter. In the early spring, you can clean them, cut entrance holes in them for the martins, and a clean-out hole in the back for you to remove the gourds' innards. Use the new semicircular entrance hole to discourage starlings from taking over the nest. Starlings are an invasive species who sometimes take over martin houses.
Animal-Shaped Birdhouses
There's a whole line of ceramic birdhouses made in the shape of fat birds. Chubby Cardinals, bluebirds and roosters have holes in their chests allowing birds to nest inside. There even chubby squirrel birdhouses. One amusing birdhouse even has the birds flying into a cat's mouth in order to access the nesting area. If you're good with pottery, you can design your own ceramic birdhouse.
Build a Planter
Join two birdhouses together with a planter box. The plans call for two regular birdhouses built facing out with a planter built between them. It only requires minimal carpentry skills to assemble this birdhouse planter. With drainage holes in the bottom of the planter and the birdhouses, rainstorms are not a problem. Use cedar for outdoor durability. After you've finished building your birdhouse planter, fill it with trailing plants, and hang it in a sunny place. Because of the closeness of the two birdhouses, both may not be occupied at the same time. Alternatively, you may attract two different species of bird who don't feel competitive with each other, such as a wren and a chickadee.
Be Creative
Use an old rubber boot hung underneath a squirrel baffle to keep the rain out. Just cut a 1 3/8-inch hole in the side, and drill a few holes in the bottom for drainage. Drill a hole both sides of the boot near the top, threading the holes with a boot shoestring. Hang the boot close beneath the squirrel protector to prevent water from entering it. Or make a birdhouse from a coffee can with a plastic lid. Just cut a hole in the lid large enough for the bird, nail the coffee can to a tree or a shed and place the lid back on the can. Use a hot glue gun to seal the lid on and, once it's hot, run the hot glue gun around the edges of the hole you cut in the lid to smooth the edges. Make a birdhouse out of a plastic milk jug or soda bottle by cutting an entrance hole and drilling some drainage holes. You can paint the jug any way you like.