It sounds corny, and God knows I've mentoned this before, but the best study aid I ever used was to make a set of flash cards based on my ground school material, the FAR/AIM, and sample FAA written exams.
First of all, I find writing or typing something really helps me remember it.
After I made them, I kept a stack of index cards with me almost always. I'd go through them at lunch breaks, on the bus or train, you name it.
I would've aced my written, but I got one question wrong, mostly because I checked the wrong multiple-choice box.
which proves that although you can enhance your memory, getting actually smarter is another matter...

this gives me an idea: I should scan a bunch of them (some have pictures), and post a question here now and then... hmmm...