Django-oembed - Project Hosting on Google Code. OohEmbed.com - your one-stop oEmbed provider. Embedding third-party content in your site using oEmbed. There's a whole class of 'Web 2.0' technologies that have emerged recently which have some common features: They solve a simple problem, they do so in a decentralised way and they stay simple.
As examples I'd quote things like XFN, OpenID, oAuth and even things like RSS and Atom feeds. They start off by solving a particular use case, and stay as simple as possible (or at least should - I'm looking at you OpenID). The latest such technology to interest me is oEmbed, via a blog post by Ben Ward. The name is a bit cryptic, but the use case it addresses is one of embedding content from one site into another.