This app was mentioned in 8 comments, with an average of 2.00 upvotes
If you like to memorize words this is my favorite free app: https://play.google.com/store/apps/details?id=com.hyperlearning.russian_en
The first time, it took me 220 hours over a period of months to pass all 5000 words. Now I'm in my second go-round, I am 30% finished and have probably spent 7 hours. So, I can feel the progress. Many words have moved from the "I recognize this word but cannot use it" category, to the "I read and understand this word automatically without effort", to the "I can use this word in speech" category. It feels good.
I also spend a lot of time listening to podcasts with transcripts, online tests, etc.
THis free app: https://play.google.com/store/apps/details?id=com.hyperlearning.russian_en
Really helped me increase my reading speed and become an automatic reader. You have to tweak the settings a bit, turn off hints and inverted hints and UFO's, AND: ignore the linear order of the app and do all of the levels at once, using only the levels with even-numbered scores. This will ensure you will have an English word in a the middle of the screen and have to choose the correct russian word from a selection of ten Russian words which float around the screen, ensuring that you have to read them again and again quickly. I have completed ten repetitions of these 5000 words and am now on my second time. A lot of these words are in my passive vocab now and are being transferred to active as I encounter them in songs and stuff.
I would like to also recommend a fun app with is all in Russian cursive, but I just replaced my tablet and sadly have lost it. I would recommend searching the app store for any kind of Russian vocab game that is in cursive. There are quite a few of them.
I have recommended this one before: https://play.google.com/store/apps/details?id=com.hyperlearning.russian_en
The reason I recommend it is because I own many vocabulary apps, and all of them bored me after a while, but i stuck with this one long enough to finish all 5000 words, and I'm now on my second go-round with it because it's fun.
I see these words everywhere, too.
This. https://play.google.com/store/apps/details?id=com.hyperlearning.russian_en
I love this app so much. I have never paid for it. I completed all 5000 words once -it took me 200 hours, I started when reading cyrillic was really slow for me. Now I'm on my second time and I'm so mcuh faster. Because it's fun. I only use it on the even-numbered levels where all of the bubbles are Russian words, and I skip around the different levels to do so. Also, I turn off the spaceships and the hints.
I lack self discipline and have a hard time studying unless it's interesting to me somehow. I found "Roots of the Russian Language" really interesting when I spent 200 hours (no kidding, the game scores the time you spent on it, so I know) learning the 5000 most common Russian words on an app of the same name. The book became interesting after I had learned enough words to want to figure more words out, kind of like a puzzle.
This is the app I used, if anyone cares, https://play.google.com/store/apps/details?id=com.hyperlearning.russian_en I have never paid for it.
Since you mentioned having a tablet, I recommend this free app: https://play.google.com/store/apps/details?id=com.hyperlearning.russian_en
Some of the English translations are wonky, (e.g. "whence" for откуда) but the point it, it was fun, and I am on my second round of memorizing 5000 Russian words, and my reading speed is near-automatic. More importantly, it helped me memorize a lot of prefixes, suffixes, and roots. I looked up a lot of my questions in this book: http://www.amazon.com/Roots-Russian-Language-Lynn-Patrick/dp/0071841342 Which you can find a torrent of, easily. Good luck, and have fun!
You can disable the audio for this vocab game: Learn 5000 Russian Words.
This is only good for vocabulary, but it is fun and addictive. And free
https://play.google.com/store/apps/details?id=com.hyperlearning.russian_en
For memorizing case endings I like Yakz