There’s now loads of great examples of ExtJS on the net. I’ve compiled a list of them from searching the forums, so enjoy:

General Apps

• CRM : [ demo ]
• Ajax Yahoo IM : [ demo ]
• Mail Center (Webmail) : [ demo ]
• File Sports : [ demo ]
• SeeMe (using Google Maps) : [ demo ]
• ExtPlorer : [ demo ]
• Group Office : [ demo ] (demo/demo)

Development Tools

• CMS : [ demo ]
• Animation Tool : [ demo ]
• Image Editor [ demo ]
• Image Editor [ demo ] : [ project page ]
• Designer Toolbox [ demo ]

Books

• ExtJS In Action [ link ]
• Learning ExtJS [ link ]