It all depends on what you want to pay, some folks get an idea in their
head and either have the machinist skills or the deap pockets to see a
project through. Often the result is not nearly as good as expected,
sometimes there are gems.
The main thing you run into is every camera manufacturer has a
different distance from the rear element to the film plane (thickness
of the camera body is another way to look at this. Canon bodies are
short so a lot of lenses can be adapted to them, Nikon & Pentax  bodies
are long so it is difficult to adapt lenses to them. Pentax has a lot
of 42mm screw mount lenses out in circulation that fit, so really Nikon
is the most difficult to adapt lenes to. Almost anything can be adapted
to Leica screw mount or M-mount.

Movie lenses are another story, c-mount lenses have an extremely short
rear element to film plane distance,and very narrow coverage. So they
are very difficult to adapt to film cameras. Though I bet they would
work with a P&S digital camera, here you just need the machinist
skills, and be willing to put up with a lack of automation. One problem
is now all the bodies and lenses are plastic. A lot of the 10x C-mount
zooms are very substantial brass lenses and are extremly heavy.

I have 2 hybrid lenses one is a Fern-Kilar 400 mm f5.6 in Leica
Visoflex mount, for this lens adapting is easy and I have adapters for
Canon FD and Nikon, both are flawed, the canon doesn't quite focus to
infinity, while the Nikon focuses beyond infinity, such are the
problems you run into. The other lens is a Kilar 40mm in a fixed Canon
mount, haven't seen a listing for this lens anywhere, a very
professional job. These lenses are both manual diaphram lenses so they
are not automated. Leitz Visoflex lenses can be adapted to just about
any DSLR lens mount by already available adapters. Mount to mount
adapters are available (cheapest) on Ebay and at www.Cameraquest.com.

Tom