After experiencing some pain with getting a clean export of node package data into CSV (JSON output from knife is hard to parse!), I put together this quick tool to do this for me.
To get a list of all the packages installed on all your nodes registered to your Chef Infra server, you can run this fun command : knife search node 'name:*' -a name -a os -a os_version -a packages -F j > nodeinfo.json
There is probably a better way to run this, but this works for me and provides some additional info like OS and version. From here, to get a useful CSV representation of this (for filtering and doing whatever Excel black magic people do) you can use Julienne:
julienne -path nodeinfo.json -output nodeinfo.csv
The makefile is pretty self explanatory, but the TLDR is :
make build-windows (builds for Windows)
make build-linux (builds for Linux)
make (builds for OSX)
This application serves a direct need for me, YMMV