Appcasting is the practice of using the 'enclosure' feature of RSS 2.0 feeds to deliver updates and release notes for new software applications. The name Appcasting is by analogy with Podcasting, which is the practice of delivering audio files as RSS 2.0 enclosures.
The idea is this: the developer publishes an RSS 2.0 feed, each item of which describes a new release of a particular software product. The items' descriptions may contain release notes or other information about what's new in this release.
When your users are using RSS aggregators which support the RSS 2.0 enclosure feature, it becomes trivial for them to keep up to date with your software releases. Aggregators such as NetNewsWire 2 support downloading of enclosed content right in the aggregator.
It's easy. There's really nothing technologically new here beyond RSS 2.0 itself. All you have to do is create your feed and in each item include a line like:
<enclosure url="http://example.com/MyApp-1.2.dmg" length="1048576" type="application/octet-stream" />
In the example, the url attribute is the direct download URL for your app, length is the length of the file in bytes and type is the file's MIME type.
Andy Matuschack's Sparkle framework is a complete Software Update framework that uses Appcasts to update applications.
Yes! Here are the ones we know of already:
Using Appcasting to deliver your updates? Let us know and we'll add the feed here: info at connectedflow dot com.