If you want to have a play with medium format without breaking the bank, the Lubitel 166 is the solution.
A Russian copy of a Voigtlander camera designed in the 1920s, you can pick them up on ebay for £20-30.
The Lubitel takes 6x6cm 120-format roll film which can also be used in 6x4.5cm format if you fit a little blanking frame (which will be supplied with the camera if you are lucky).
The camera is at once delightfully crude and fiendishly clever. It's 100% manual, so you'll either need to use an external light-meter or simply use the 'sunny 16' rule. Although you can theoretically focus visually, you're better off pacing out the distance and setting that manually too: even using the flip-out magnifying glass, the focusing screen is not the camera's strong-point. But the twin-reflex geared focusing system is still theoretically very clever: twist the upper lens to focus on the viewing screen, and that twists the main lens to set the same focus for the film.
Ironically, the crudeness of the lens is one of the most appealing things about the camera. The circular distortion lends images a lovely soft and romantic feel - see the samples below. The other appeal is the back-to-basics nature of it: no electronics, no metering, no automation, just you and the photo you want to take.
