Keikai is designed and architected for big data. With frame-based rendering and super light-weight data structure, it is the fastest web spreadsheet regardless of size.
SheetAside is Chrome Extension. It allows you to access your Google Sheets from any tab, with a right-click. Can be used for manual leads collecting, research, and vocabulary building.
TotalSheets is a platform that offers you all the tools you need to create a fully functional online spreadsheet. Similar to Google Sheets in concept, but with the intention to give a greater control to owners over the appearance of their published spreadsheets.