Recently I stumbled upon this interesting blog post Windows Phone 7 with Twitter which showed how to use oAuth on Windows Phone 7 but it was unfortunately built with the beta versions of Windows Phone 7. As an exercise I decided to upgrade the code to get it to work with the RTM release.
Some things which needed fixing or which bugged me during the upgrade
Be carefull about some changes in the APIs - WebBrowser is now a sealed class. You cannot inherit from it. IsScriptEnabled, Source, and Base are now dependency properties. NavigatedEventArgs change to NavigationEventArgs.
Changes have been made to WMAppManifest.xml - http://10rem.net/blog/2010/09/16/announcing-the-windows-phone-7-release-wp7-silverlight-toolkit-and-xna-40 – you can find this xml underneath the properties folder in your project
This will probably get you going … have fun