Sheetsu - Turn Google Spreadsheet into API
Grist - Grist makes it easy to transform spreadsheets into a custom database where data is truly actionable.
SpreadSimple - A blazing-fast way to create and manage sites using Google Spreadsheets
Rows - The spreadsheet where teams work faster
SheetAside - Access your Google Sheets from where you are
UProc for Sheets - Boost your sales, marketing and IT tasks from Google Sheets