One of the major areas that I need to improve to pass the Japanese Language Proficiency Test (JLPT) N3 this year is my reading speed and accuracy, which means I need to really be able to look at kanji and just know the meaning fairly instantly. I've started getting serious about using several different study tools, and I think coming at the challenge from different angles is really helping! In the past I've tried Remembering the Kanji (Heisig's classic method), so I'm continuing to learn these helpful meanings with some great study goals available on Smart.fm. These word associations really help, but I've found I still need some solid brute force pattern recognition as well, so I'm also using Read the Kanji (which I can't recommend enough) as well as several iPhone apps to kick my brain into gear! I love it when these different methods seem to synchronize and reinforce each other.
My favorite is Japanese Flip, which focuses on kanji compounds. This is fantastic since I get to exercise my vocabulary as well as my kanji recognition! Japanese Flip works on a kind of honor system where you look at the Japanese, think the answer to yourself, and then honestly respond if you were right or wrong when presented with the correct response. It does a great job with advanced spaced repetition, and it's super-fast to launch and whip through a few words during any spare moment.
Next is KanjiBox, which uses a more traditional multiple choice interface where you choose the kanji combination based on a presented word definition. This app allows you to study individual kanji as well as vocabulary, and displays cool progress charts to help you decide what to study next. I really like that when you make a mistake, it displays the definition of both the correct and incorrect answers!
I've also been playing with iKanji Touch, which has the most elegant and beautiful interface design, but doesn't let me plow through kanji at the speed I like. Everything about this app is top notch, but for me it's just a little too thorough (which is probably by design to facilitate really solid learning). However, it's still a fun app and a really valuable tool to have in my study arsenal!