Hello list,
for a long time I wanted to contribute to an open-source project and
because of my liking for compilers and in particular the nice approach
of Clang, I decided that I want to contribute to your project.
Since I am new to the project and its internals, I would like to ask
for guidance. My preferred field of work would be to enhance Clang on
Windows, but if necessary (or more convenient) I'd be happy to take on
other challenges. I am proficient in C and C++ as well as other
languages. Currently, I have no clear picture of what needs to be done,
where to start and what to do.
I know that my approach is not the best approach, but I hope that
someone can point me in the right direction so that I and you may
evaluate whether I can contribute anything of value to the Cfe project.
Thanks in advance,
Philipp Berger
Hi Philipp,
Both attitude and experience counts as very positive, and you seem to
have both! 
If you look for "clang windows" on our bugzilla (http://llvm.org/bugs)
you'll find plenty of things to do. One way of doing it is going
through the list, picking something that you think you can do,
investigate, discuss. Another thing is to search for the same topic on
the mailing list, and see who are the people that more often work on
Clang/Windows and engage on the list or IRC (OFTC/#llvm), find things
that are not documented but would be cool to have, etc.
You don't need any special permission to work on Clang or to send
patches, or even to review patches, if you feel inclined. The only
thing to remember when reviewing is that the phrase "looks good to me"
(often abbreviated LGTM) tend to be interpreted as "an approval to
commit", so you should only say that when you become a maintainer of
part of the code.
Have a look at the developer's policy for more info at
http://llvm.org/docs/DeveloperPolicy.html
And welcome to Clang/LLVM! 
cheers,
--renato