how to create new facebook apps?

[ken steve]

hello friends i am interested in doing a facebook application...as my major project.......actually we are planning to desing for marketting purpose.....we create a new site and embedd this app there by providing a login....so when a user registers to this site with his facebook and twitter account or something else.....if he write something in the site.the message should reflect in his both facebook and twitter accounts....that is the idea..........plzzzz somebody guide me in this aspect....i have lot of hopes on this project...............somebody give me suggestions or links that will be useful for me in designing.....regarding the programming linking etc...................i will be extremely thank ful to u.thank u