Sheetsu - Turn Google Spreadsheet into API
Publisheet - Publish your Excel sheets to the web as dynamic web applications with formula support.
SpreadSimple - A blazing-fast way to create and manage sites using Google Spreadsheets
CALCONIC_ - Build & add interactive calculators to your website! Choose from more than 50 premade calculators or build your own from scratch. No coding required. Free plan available. Zapier Integration. Publish Anywhere.
SheetAside - Access your Google Sheets from where you are
SpreadsheetConverter.com - Use online spreadsheets, smart forms and beautiful charts in your blog or website. Put your booking and order forms online. Show live charts. Change any cell and the online spreadsheet or live chart immediately updates itself.