Google Drive - Sheets web based spreadsheet from Google.
Zoho Sheet
Free
Zoho Sheet is an online spreadsheet application that lets you create, share, collaborate and publish spreadsheets from anywhere.
EtherCalc
Open Source
EtherCalc is an opensource web spreadsheet.
Compare Gnumeric with alternatives
Compare Google Drive - Sheets and Gnumeric and decide which is most suitable for you.
Compare Zoho Sheet and Gnumeric and decide which is most suitable for you.