I got really obsessed with freelensing for a while. Freelensing is a technique in which the lens is detached from the camera and tilted. Tilting the lens results in lots of bokeh and light leaks. I really love how these images turned out.
I use a Nikon digital camera with D lenses, and there's a little extra step that has to be taken in order for this to work. On the inside of the lens, there's a little lever. This lever controls the aperture, and when the lens is detached, the lever closes the aperture. So, I had to find something small to hold this open. I tried to hold it open with my fingernail, but that was beyond awkward.
This technique works best with a prime lens. You also have to get really close to your subject. If you are using a camera other than a Nikon, check out this post for help with your specific camera brand.