Please note: I do not own and have not paid for anything listed below. They can be found open access on the internet.
As always, use the past exam questions on the official College Board website. (They are not included in the link above).
Albert: subject explanations, practice sets (paid), blog, etc.
Heimler's History: useful FRQ writing tips.
PBS U.S. History: helpful videos, articles, and lessons for U.S. History
Sometimes watching documentaries can be a relaxing way to recap material. I recommend "The Story of US" or "America in Color". You can do several things while watching:
Note down what you can or cannot recall - this helps with finding areas of weakness
Store relevant historical events in your head - you might find them handy when writing 'outside evidence' in DBQs
Note the connections between events (cause-and-effect, one-cause-in-many, etc.). This is something you should do constantly, not just while watching or reading. You must get into the habit of linking events in your head. If you don't know what to review, connections should always be your first choice.