Sparkle 1.0

Sparkle is a module that developers can stick in their Cocoa applications (five-step install!) to get instant self-update functionality.

By that, I mean that your app will be able to update itself, not just check for new versions: it'll read the update information from an appcast on your server, download, extract, install, restart, and even offer to show the users release notes before they decide if they want to update.
It's free, it's easy, and it'll make using a Mac better for everyone, so go for it! Make sure to visit Sparkle's homepage to see a video of it in action.Features
- True self-updating - no action required from the user.
- Supports appcasts for release information. Appcasts are cool.
- Extracts updates from .tar, .tbz, and .tgz archives.
- Displays a detailed status window to the user.
- Can display release notes to the user before updating.
- Seamless app integration - there's no mention of Sparkle anywhere; your app's name and icon are inserted everywhere automatically.
- Really, really easy to install.
- You don't have to put any glue code for Sparkle anywhere in your project (it's all through IB), so it's trivial to upgrade or remove the module.
- (Should be) good about error handling in bad conditions.