JQuery
JQuery UI
JQuery Mobile
Although it is designed for mobile apps, it could be used for desktop apps too. It is in a sense much more modern than JQuery UI with wider industrial support and relies on CSS3 more. One can even wonder why JQuery UI does not migrate to JQuery Mobile.
Frameworks
In order to select a framework, it is important to understand the criticism on MVC such as the one by Michel Beaudouin-Lafon.
Single Page Application
Other