Levels of classification over Top Secret:

1. Sensitive Compartmented Information" (SCI)
2. SCIF data or information that can only be read inside of a Special Compartmentalized Information Facility. 
3. Special Access Programs (SAP)
4. SCI Access" or SAP approval

   In the military, all classified information is divided into one of three categories:

   CONFIDENTIAL: Applied to information or material the unauthorized disclosure of which could be reasonably expected to cause damage to the national security.

   SECRET: Applied to information or material the unauthorized disclosure of which reasonably could be expected to cause serious damage to the nation
   al security.

   TOP SECRET: Applied to information or material the unauthorized disclosure of which reasonably could be expected to cause exceptionally grave damage to the national security.

ref: http://usmilitary.about.com/cs/generalinfo/a/security.htm