The National Institutes of Health (NIH) announced that beginning with applications due on or after September 25, 2013, NIH will require all applicants to use new electronic application forms called FORMS-C (with the exception of select application types). You can read the detailed notice at: http://grants.nih.gov/grants/guide/notice-files/NOT-OD-13-074.html
The updated forms will be incorporated into new and existing Funding Opportunity Announcements (FOAs) beginning this July.
NIH created a two-page summary of changes to the application forms here: http://grants.nih.gov/grants/ElectronicReceipt/files/FORMS-C_Changes.pdf
Multi-project applications that are transitioning to electronic submission beginning with the September 25, 2013 due dates (see http://grants.nih.gov/grants/guide/notice-files/NOT-OD-13-075.html) will also use FORMS-C packages.