Google is great, it’s a fact.
Today they have launched an Ajax Library API. They are hosting the major Javascript Libraries (Jquery, dojo etc), and are providing a nice API to load them in, pick your version number etc.
They also serve it over a content delivery network, which means when a user requests the library file the server will send it from the nearest server to the user so it loads in nice and quick. The CDN is also setting the caching headers correctly and gzip the files for speed.
The other huge advantage to this is that as the files are being delivered from the same place for every website that uses this api (and being google lots of people will use this api) the selected library will be cached on the users computer and won’t need to be downloaded again.