Sheet protection in Google Docs spreadsheets

You can now control who can edit individual sheets in a Google Docs spreadsheet.

Editions included:
Standard, Premier, Education, Team and Partner Editions

Languages included:
All languages supported by Google Docs

How to access what's new:
To protect a specific sheet, select the sheet and click the down arrow next to the sheet's name, and select the 'Protect sheet' option. Next, select who is allowed to edit the sheet from the 'Protect sheet' preferences box.

For more information:
http://googledocs.blogspot.com/2009/04/sheet-protection-gives-you-finer.html