This is list of New Applications and Defaults on ubuntu 11.10 (Oneiric Ocelot)
Thunderbird is included as default email client including menu and launcher integration.
Déjà Dup is included as the default backup tool, making it easy to upload backups to Ubuntu One.
The new Gwibber landed in Oneiric bringing improved performance and a new interface using the most recent GNOME technologies.
GNOME got updated to current unstable version (3.1.5) on its way to GNOME 3.2
LightDM now uses the new Unity greeter by default.
Software Center updates
The Ubuntu Software Center adds new "top rated" views to the main category page and all subcategory pages, now allows you to edit or delete your own reviews, and has had a significant speedup for standalone deb file installations (gdebi functionality).