Museums are often considered a staid affair: Visitors walk through walls lined with paintings, sift through historic documents, or look at artifacts behind sheets of glass. But some institutions stray from the norm and offer more than your textbook visiting experience. Whether you're browsing terrible paintings at Boston's Museum of Bad Art, or encountering life-size aliens at New Mexico's UFO Museum & Research Center, you'll find yourself enlightened--and entertained. Here are our picks for America's most unusual museums.