Mathematica 6 introduced the revolutionary idea of symbolic dynamic interactivity. Mathematica 7 makes use of this idea throughout the system, and adds a number of additional features to the core concept.
Manipulate (modified) — new support for arranging controls in grids etc.
Control — an interactive control with type automatically chosen
ButtonBar — a bar of buttons with labels and actions
ChoiceButtons — a pair of OK and Cancel buttons that close a dialog
Pane (modified) — scrollable pane
TabView (modified) — scrollable tabs
Panel (modified) — display a panel with different appearances
PreemptProtect — protect evaluation from interruption by preemptive evaluations
Placeholder — symbolic representation of place to type into