Google Summer of Code 2012 project, GHCi for the web
The prototypes subdirectory contains several quick hacks demonstrating various concepts.
prototypes/hintdownload/ is the example.hs from http://code.haskell.org/hint/devel/examples/ modified to download and execute Demo.main from http://www.scannedinavian.com/~shae/Demo.hs
prototypes/scottywebexecute/ is examples/basic.hs from https://github.com/xich/scotty/ modified only slightly to prove to myself that I understand the code.
prototypes/hintdownloadexecute/ is the front end from http://haskell.handcraft.com/ modified to have scotty and hint as a backend instead of calling tryhaskell.org