For more music theory practice:
 
www.musictheory.net -  "Lessons" are like tutorials for certain subjects we have covered in class.  "Exercises" will help you practice concepts covered in class.  Exercises can be customized to help you focus your practice on topics you really need to work on.
 
www.gmajormusictheory.org -  This site gives you great resources to hear the concepts we have learned performed within actual pieces of music.  It also has basic concept drills and games.  Look under "Music Theory" - "Harmonic Dictation" for step by step guidance for the Harmonic Dictation portion of the exam.
 
apcentral.collegeboard.com - This allows you access to the Free Response and Sight Singing questions from the last 18 years.  You can see/hear the questions, answers, audio prompts, scoring guidelines, and sample responses for all of the questions.  This is a GREAT tool when preparing for the AP Exam.
 
www.teoria.com - This site allows you to practice Rhythmic Dictation, Melodic Dictation, a little bit of Harmonic Dictation, as well as other lessons and practice.  Also able to be customized.
 
www.noteflight.com - VERY convenient online notation software.  Free memberships available.   
 
Staff paper sources - www.blanksheetmusic.net