The Ultimate Google Sheet Toolkit - We put together a curated list of templates, videos, and tutorials that can help you build your analytics expertise.
Sheetsu - Turn Google Spreadsheet into API
MadKudu for Google Sheets - Get predictions about your target market in GSheets for free
SpreadSimple - A blazing-fast way to create and manage sites using Google Spreadsheets
SyncWith for Google Sheets - Data from any app into Google Sheets, reports & dashboards
SheetAside - Access your Google Sheets from where you are