If you shoot ARRIRAW or ProRes, the Amira Color tool is a straightforward, easy to use tool for creating ASC CDL and LUTs for different looks you create. It is a free download after registration at the ARRI Amira webpage. There is also a video posted on YouTube that covers its functionality. It is a subset of what Assimilate Play offers due to the limited codec support, but is easier to use for those who are dabbling in ASC CDL/LUT world for the first time.
I did a quick test to see how it might fit into a Media Composer workflow (v7.x and later) with ASC and CDL support. Unfortunately, as with Assimilate Play, the ASC CDL export will not work with Media Composer as it is XML and Media Composer imports its metadata as ALE or via an AAF. Also, the XML is rather limited as it does not even list the file to which the values should be applied.
The creation of looks and exporting as a LUT does work as long as you export in a .cube LUT format. The following chart shows which exports worked and did not (Green = Yes, Red = No).
All .cube LUTs except for FilmLight imported into Media Composer. I am impressed at the number of LUT types it does support - I was also able to import one LUT type and save it out as another which would make this a nice LUT translator, but I need to more testing to ensure it did not change anything looks wise.It would be nice if it had a timecode display as well. But this is a nice little tool to have on hand for quick Look -> LUT generation, as well as apply LUTs quickly to ensure they are correct when created elsewhere. It is available for OS X only, 10.7, 10.8, and 10.9.