Sheety - Turn any Google sheet into an API instantly, for free. Power websites, apps, or whatever you like, all from a spreadsheet. Changes to your spreadsheet update your API in realtime. Neat
Reflection - Market insights for app developers
SheetBest - Turn a Google SpreadSheet into a JSON Database API
Peek-a-week - Look back at your week to see if you were productive
Sheetsu - Turn Google Spreadsheet into API
Corus - A market for survey data and research insights