Here is a list of my favorite features that you will find in Snow Leopard:

• Faster Wake up, shut down, and joining a wireless network.
• Automatic Automatic Automatic! Snow Leopard automatically detects your current time zone and will update printer drivers so you don’t have to.
• Safari is super fast in Snow Leopard. It’s also super resistant to crashes (Damn browser plugins, ahem, Flash).
• Built in Microsoft Exchange support right out of the box. Great for students and organizations utilizing Microsoft Exchange (almost everyone). Email, Contacts and Calendar with Exchange will work the way they are supposed to without any extra setup.
• Exposé and Stacks get new functionality. Exposé will now utilize the dock for a better user experience (just click and hold on an application icon and all windows will unshuffle so you can quickly change to unshuffle another one). Stacks are now scrollable and gains navigation.
• Grand Central Dispatch! For us developers this is simply awesome. It makes it super easy to take advantage of multicore processors. Consumers will also notice a kick-ass difference in application performance by applications utilizing this technology.
• OpenCL, yet another geeky technology. When an application needs extra processing power it can turn to the graphic processor to share the load. Another piece of technology to make your mac scream in terms of performance.
• 64-bit native applications including Finder. Speed!
• Reclaim your storage! Not only will installing Snow Leopard be 45% faster than it’s predecessor, but it’ll give you about 6 GB of storage back!

Traditionally Apple charges $129 for new versions of OS X, however this version is so important that they want everyone to upgrade and it’ll only cost them $29.