kANBN is yet another task management tool. But you'll love this one and I'm going to tell you why. It's pretty simple. You can create boards in which you create cards. You also have the ability to add to do-lists to every card.
And the best thing is: It's got drag and drop! Now I've got you, huh? Why don't you give it a try? There are no ads and it's absolutely free.
Also, if you feel like using it on your computer, too, you can just visit http://kanbn.net and sign in with your account. And it's optimized for tablets!