Two of the new features that were introduced in Internet Explorer 8 Beta 1 were so called Webslices and Activities. The first introduced a way to keep track of little pieces of information that could be subscribed just like RSS while the second was an interactive context menu with actions like dictionary searches or digging an article.
I was actually pretty sure that the second option was more or less already implemented in Firefox, the first however seems to be quite useful. It’s possible for instance to add stock charts or a price of an item in a browser bar to have it always in sight.
Webslices are emulated by the Firefox add-on
Webchunks while the Activities are still called
Microsoft Activities. Both are said to work with the latest version of Firefox 2 and even the beta of Firefox 3.
Not a lot of websites are offering
webslices at the moment. The Microsoft website lists four: Facebook, Ebay, Stumbleupon and MSN. The same can be said for
activites, about ten are available on the Microsoft website.
Webchunks:
Microsoft Activities:
Will you install one or both of the extensions ? Via
Mozilla Links Webslices and Activities ported to Firefox
Webslices and Activities ported to Firefox 
Linear Mode
