Objective-C Social Networking General Question

I've been developing application for Iphone and now I want to try to create appplication like social bookmarking but I didn't really find any help on the net. I will have a create a login/pass, retrieve data and display开发者_StackOverflow them. So I want to know what do I have to use to implement all of that for any social bookmarking website. If you have suggestion, idea, tutorial, you are welcome.

thanks,

Most of the major social networking sites have API's for coding against their services, for instance Facebook and Twitter.

I'm sure there are other API's available, so it's just a matter og Googling for them using something like " social-network-name API developer" as serch criteria.

Claus

Wouldn't it be easier to integrate with an existing one?