Will you be posting tweets on the application’s behalf or on behalf of your users? If you want to offer a simple way for your own users to Tweet from your site without having to learn about authentication, check out [node:183,title=“Web Intents”].
As for the copying and pasting in the browser/PIN input/etc comment about OAuth: for a web-based application, it’s much simpler than all that. Especially if you’re using a library like Twitter4J. Your server issues a request to Twitter. Your server redirects the user to Twitter’s OAuth screen. Twitter redirects the user back to your server. You issue another sever-to-server request to Twitter to obtain the user’s authorization and then you’re done.
But if you’re looking for the simplest possible integration points, Web Intents are a good fit. They’re just links.