Speed Dating is one of my go-to structures, like War and Solve Crumple Toss, for incorporating lots of practice with built-in behaviors to encourage learning. It hits all my requirements for a practice activity: it's self-checking, promotes dialog, allows for some differentiation, requires a little movement, and the kids are doing all the work.
To prepare, you will need cards or slips of paper with problems on one side and the answers on the other. (Here are 16 Rational Expressions cards with answers and here are 15 Probability & Permutations cards with answers you can cut out, fold, and use.)
It's important to use problems that will take all your kids about the same amount of time to complete. To differentiate, use a mix of difficulties. If you will have the whole class working together, you need as many problems as students. If you are breaking the class into two distinct groups, you need half as many problems as students, but two copies.
Arrange your desks in two rows facing each other, like this:
They have several minutes to solve and become the expert on that problem for the day. After a few minutes have passed, tell them the answer is on the back so they can check if they did it right.
When ready, the students trade problems with the person across from them and work it. If they have a question, they are looking at the expert on that problem. If someone raises their hand to ask me a question, I first ask the expert student, "What is his question?" If she says "I don't know," I tell them I'll be back around in a few minutes.
When ready, students get their original problem back (you will have to remind them to get their original problem back before shifting seats for a while, until they get used to the structure.) One row stands up and shifts in the same direction. The student on the end that gets bumped off circles around to the other end. Now everyone should have a new partner and trade problems.
Repeat until all possible partners are exhausted or you run out of time.
This was christened "Speed Dating" by my third period trig class last year. Another class I had called it "The Math Train." If we haven't done it in a while, kids start asking for it. The social component makes it fun, whatever you call it.