The XPages ExtLib (latest releases / info can be found on openNTF.org) offers a huge amount functionality including mobile controls that look like iphone / android controls when viewed on a mobile device, as well as social integration with facebook, twitter etc.. The ExtLib library also comes with 2 updated templates (discussion / Teamroom) which show off the new controls and have mobile front end.
These controls allow you to have mobile and desktop based web applications all coming from the same code which can be a huge bonus