On the LLVM homepage is a link "Browse ViewVC" which points to http://llvm.org/viewvc/llvm-project/ Currently this link results in 404. The same is true for various LLVM sub-projects, e.g. clang's http://llvm.org/viewvc/llvm-project/cfe/trunk/ or libc++'s http://llvm.org/viewvc/llvm-project/libcxx/trunk/ The "Browse SVN" links work.
ViewVC was temporary disabled to to excessive DDoS which hogged the whole llvm.org. We're considering the alternative to this service now.