Maddavo's Market Share (MMS) is a data store for Elite Dangerous market prices, stations and systems. The project started in October 2014 as a price sharing tool for TradeDangerous users. Prices are accepted from users by direct upload and then merged into the database. Prices files are then generated for users to download.
As more stations were discovered, the ability to upload/download Station.csv files was also added. Further updates were added to incorporate live data from EDDN. Station data is also syncronised with EDDB every 24hrs.
In June 2015 a very large upload of stations was performed by @Anthornet which pretty took the station list from 50% to 99% of all stations in the game. Data for those stations continues to be added.
The data can be downloaded directly from the website, but most users download the data using the Maddavo plugin for TradeDangerous. Users can also upload their TD .prices file (using TD) but most users use a tool to capture prices which is then sent via EDDN.
Shipyard data is captured from EDDN and available in TD format ShipVendor.csv .
Also check out the other tools mentioned on the site like the online version of RedWizzards tool to calculate coordinates for new systems.
... and yes, this is the "Maddavo" wanted throughout the galaxy for Stellar Graffiti.
21st Sept 2016: UPDATE - MMS now supports EDDN's Commodity 3 schema.