I am trying to send the url to twitter, make sure you also set the Bit.ly account setting in the ShareKit configuration, otherwise you will get the message MISSING_ARG_APIKEY added to what you are tweeting.
Edit: There should have been a comment above. For callback URLs - set it to anything, it will not actually be used. On the Twitter page where you created the application (and got your key and secret), make sure that you install the application as a browser application, not a client application, and it displays a field for the callback URL. Then in the Sharekit configuration, just put the same URL that you specified in the details of the application. I just used my own website address. The Sharekit documentation says that the URL will never be visited, you just need to know it, so when the web browser displaying OAUTH is sent to that URL, Sharekit knows that the login is complete.
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