This new add-on helps to create iGoogle like widgets from any portion of any web site.
Main idea of PageSlices is possibility to see parts of web sites together. You can select a block of information from any site and store it in your page along with another blocks. Then you will always see an actual information from source sites in one page.
All your pages with blocks are stored on PageSlices.net site, so you can get an access to them from every computer having Firefox installed.
Check out a short video introduction at http://PageSlices.net
or tutorial at http://PageSlices.net/Home/Tutorial