From the WSJ:

Google Inc. plans on Tuesday to release a Web-based spreadsheet application, according to people familiar with the matter.

Google Spreadsheet, which will be made available on a limited test basis, follows Google's March purchase of a company offering a Web-based word processor called Writely.

The two Google Web-based applications represent possible challenges to Microsoft Corp.'s core personal-computer software business. Microsoft's Word and Excel dominate the word processing and spreadsheet markets.