Latin and Greek

Latin and Greek
Textkit (Greek and Latin grammars, readers, and answer keys)

Latin
National Archives Beginner's Latin (not classical Latin)
Study Guide to Wheelock's Latin
Latinum
Wikibooks Latin
University of Texas at Austin Linguistics Research Center Latin Online
Latin for Mountain Men
Allen and Greenough's New Latin Grammar for Schools and Colleges
Fr. Gary Coulter Latin (Catholic)
Latin Handouts
The Latin Library

Fun Stuff
Headventureland (website of Classical Academic Press, has some Greek and Latin videos and games)
Greek Word of the Month
Latin Word of the Month

Modern Foreign Language

Spanish
123TeachMe.com  (Elementary to Adult)
OnlineFreeSpanish.com (Elementary)
Salsa (Elementary)
Duolingo (Middle Grades to Adult)