Mozilla announced Jetpack SDK 0.3 this week.
Two high-level improvements in the Jetpack SDK 0.3 are "context-menu" and the "self" API.
The context-menu API lets add-ons add items to the context menu for Web pages. This gives users additional options when they context-click on elements in pages or pages themselves. For example, an add-on might add an "Edit in Pixastic" item to the context menu for images.
The self AP enables add-ons access to resources such as: Web pages, images, etc that are bundled with the add-on package. For example, an add-on could bundle an icon that displays the browser's status bar.