From The Omni Group:
OmniDazzle is a set of fun and useful enhancements that help you highlight certain areas of your screen, create special effects, and track the location of your mouse pointer. Each plug-in can be configured to suit your own particular preferences: change colors, make objects bigger or smaller, or change the way you activate the OmniDazzle plug-in of your choice. By allowing you to manipulate your screen, OmniDazzle offers practical features for doing presentations, taking screen shots, focusing on specific tasks, and adding visual information to your desktop. This one might just eat your productivity for the entire day as you stare mesmerized at the, ahem, dazzling pixie dust cascading down your screen. Pixie Dust turns your mouse pointer into a virtual magic wand creating a spray of colorful sparkles wherever it goes. You can change your pixie dust to include only a few tiny sprinkles, or turn it into a giant firehose of awesomeness. The color range is up to you, too. Illuminate your screen with a virtual flashlight that follows your mouse pointer wherever you want it to go. When triggered, Flashlight dims your background and turns your pointer into a helpful, shining beacon that lights your way. You control the size and quality of the light, the color, and the background. This allows you to highlight areas of your screen using different shapes. Pick a shape (circle, ellipse, rectangle, or window border) to start, then move your mouse to control the size of the shape. Watch and be captivated as everything outside your selection dims. This one's great for guiding an audience during a presentation, or creating an awesomely instructive screenshot ("then click THIS button RIGHT HERE"). You can customize borders, dimness, and fill.