Wh grammar question...

Is it correct to say, "What are you doing this weekend?"
please explain why.
Thanx!

It's correct. What is used in questions at the beginning of a clause. Are must be before the subject (you) in a question. The continuous present tense is often used to denote future action. No preposition is used before this when this refers to time.
CB

Isn't it suppose to be, "What are you going to do this weekened?"
or maybe "What will you do this weekend?"

grace0513Isn't it supposed to be, "What are you going to do this weekened?"
or maybe "What will you do this weekend?"

Not necessarily but your suggestions are right as well.
CB

Please don't double post.
CB

it's my first time in here, so i thought my first post was not valid till i register first.
anyway, thanx for the answer.
But, would it also be correct if i'll say "What are you doing tomorrow?"

Yes, it's correct. Present Continuous Tense can denote the action in the nearest future and also the planned action.

Is it correct to say "What are you doing this weekend?"

That is not only correct, but it is also a very common usage.