It seems strange for me to say to a friend: "I'm going to meet you at ...".
It's as if I were telling them what to do. It's fine if the listener is your child, but otherwise? I suppose if the listener had forgotten about our appointment then it would be then possible to say:
What? Don't you remember? I'm going to meet you today at noon.
The preposition used with noon is at.
However, it is worth pointing out that not all English native speakers will say, noon. British speakers will tend to opt for midday or even lunchtime. The latter is often said, especially between employees working in the same company. Their lunchtime may or may not start at 12.00. Obviously, if they are both at their desks until 13.00 then lunchtime would be at that hour.
Therefore a British English speaker might say:
We're meeting at midday, today.
EDIT: If you have not already arranged and fixed a meeting with your friend
then Hellion's suggestion is the most appropriate one. With promises, the modal will is commonly used.
I'll meet you today at noon
I'll meet you (tomorrow/on Monday/this
Tuesday etc.) at midday
A more polite sentence is to form a request or suggestion using one of the following modals: shall, would, could, and can.
1) Shall we meet today at noon?
2) Would you mind if we met today at noon?
3) Could we meet at midday?
4) Can we meet each other at lunchtime?