Tilt-shift Photography

Tilt-shift and perspective-control lenses are available for many SLR cameras, but most are far more expensive than comparable lenses without movements. The Lensbaby SLR lens is a low-cost alternative for providing tilt and swing for many SLR cameras, although the effect is somewhat different from that of the lenses just described. Because of the simple optical design, there is significant curvature of field, and sharp focus is limited to a region near the lens axis. Consequently, the Lensbaby's primary application is selective focus and "toy camera"–style photography.
It is also possible to construct a tilt-shift lens of sorts, as described in the linked article by Dennison Bertram.