Is there an iPhone app that tells me if my contacts are iPhone users?

Certain apps I have only allow me to use them with other iPhone users. I don’t know which of my contacts are iPhone users, so is there an app that would let me identify the iPhone users?

Is there a way to sync your iPhone on a different without erasing everything?

I just got rid of the computer i usually sync my iPhone on. And, as everyone knows, the new 2.0 update is coming in very soon.
I have so many things on my iphone that i can’t get anywhere else.
Is there a way that I can sync my iphone on another computer without erasing everything [...]

What iPhone app is there which allows you to see all your contacts updates via facebook, twitter etc?

I want an iPhone app that allows me to see what my contacts have been up to and also update all my statuses at the same time, I’m sure there’s app’s out there for that, but what are they called?

Itunes help. Is there a faster way to download itunes or like a lower version of itunes?

I don’t want anything else from itunes. I already know other websites but they dont work for me either because my computer is really really slow and wont download like ANYTHING without a problem.