metapages - add your own content to web pages

Simon Wilson writes about Greasemonkey as a lightweight intermediary.

He describes using it to inject additional content on-the-fly onto webpages you are using.

The latest release of the swiss army knife of Firefox extensions adds support for cross-domain XMLHttpRequest calls from greasemonkey scripts. What that means is that you can create a user script (a short JavaScript that will be executed whenever your browser loads specific pages) that can then pull extra data in from another server. This new ability is described in the greasemonkey documentation.

found via trendalicious