I've got an idea to help deal with homeless and want to find out if
it's been done, or to find other, related ideas.  My idea is to
recruit churches and other volunteer groups to "adopt" or "sponsor" a
homeless person or family (or group of homeless folks) to underwrite
the social services they need (case management, drug treatment, etc.)
they need at the shelter they're admitted to.  The idea is not to
create a new program, but a new funding mechanism as well as a show of
support for the person - that someone in the community is investing in
them and rooting for them.

If nothing like this has been done, I'm willing to accept other
creative ideas that volunteer organizations have put into place to
deal with this problem.

A program such you have suggested is operating in many states and USA
communities, with government funds paying all or most of the
opperating costs. For some homeless and needy the government rules
interfer, so there is a need for private charities as the government
subsidised programs tend to be sub contractors to the government. Most
of the problem is: some of the homeless are not co-operative in
accepting help. Most have tried and failed, drug treatments multiple
times. Others are slightly insane (aren't most of us)such that helping
them is very time consuming, stressful and often ends in failure in
spite of intense efforts by the persons trying to help. If you have
the resources to start such a program, go for it, but understand that
it is more difficult than it appears, especially as you will be
working mostly with people who have not succeeded in traditional
government style help programs.   Neil