what are you up to?

 o que voce pensa que esta´ fazendo?

It's just an informal way of asking "What are you doing right now". See esl.about.com/library/lessons/blphrasalbuild.htm – 

Gaurav

 Sep 14, 2010 at 4:22

5

An excellent example of a sentence that's awkward to not end with a preposition: "up to what are you?" – 

Seamus

 Sep 14, 2010 at 10:15

@Seamus: True, but it's not like you'd be using this construction in a formal setting. – 

Billy ONeal

 Sep 14, 2010 at 16:10

1

@BenLee The rules of grammar Yoda does not adhere to. – 

Seamus

 Mar 31, 2012 at 13:48

1

@Seamus: I would phrase it "To what are you up," which is still very awkward. – 

John Gietzen

 Apr 21, 2012 at