Simple solution for SharePoint Foundation 2010 and SharePoint Server 2010 to allow site administrators to add the jQuery library to each SharePoint page without modifying master pages or adding it with a Content Editor Web Part.
This feature is installed to the farm and is enabled on a per-site basis. By navigating to Site Actions > Site Settings > Look and Feel > jQuery Settings, the site administrator can also configure the version of jQuery to load (1.3.2 through 1.6.1) and where the jQuery library will be delivered from (the local site or one of the available Content Delivery Networks).