GitHub is home to over 20 million developers working together to host and review code, manage projects, and build software together.
For web development especially, incremental compilation is very useful. In Yesod we have a yesod devel command that accomplishes this. We are also looking into using the shaker package which appears to use very similar mechanisms. They both use the cabal library inteface to build the packages. To efficiently use cabal-dev instead of cabal, these tools need a callable library.
We were just discussing how useful this would be.