Endogine is a sprite and game engine, originally written in Macromedia Director to overcome the many limitations of its default sprite engine.
Some of the features are:

Easy media management.
Sprite hierarchy (parent/child relations, where children's rotation, LOC etc. are inherited from the parent).
Behaviors.
Collision detection.
Plugin-based rendering (Direct3D, GDI+, Irrlicht is next).
Custom raster operations.
Procedural textures (Perlin/Wood/Marble/Plasma/others).
Particle systems.
Flash, Photoshop and Director import (not scripts).
Mouse events by sprite (enter/leave/up/down etc. events).
Widgets (button, frame, window, scrollbar etc.). All are sprite-based, so blending/scaling/rotating works on widget elements as well.
Animator object (can animate almost any property of a sprite).
Interpolators (for generating smooth animations, color gradients etc.).
Sprite texts (each character is a sprite which can be animated, supports custom multicolor bitmap fonts and kerning).
Example game prototypes (Puzzle Bobble, Parallax Asteroids, Snooker/Minigolf, Cave Hunter).
IDE with scene graph, sprite/behavior editing, resource management and debugging tools.
Simple scripting language, FlowScript, for animation and sound control.