One feature I really like with Chrome is when opening a new tab, you are provided with Thumbnails of your recently/most visited sites to select from as seen in this Chrome screenshot.

This is something that is still in development with Firefox and the developer as experimenting several ways to accomplish this. In the meantime there is Trace, an add-on which replicates the behaviour of Chrome’s new tab interface plus some other enhancements (choose from Stickies, Most Visited or Recently Visited as well as a list of recently closed tabs). The thumbnails are served by ShrinkTheWeb.com. A couple issues have been posted on AMO about this addon in regards to ShrinkTheWeb service. One being the thumbnails can at times be slow to load. You can however specify another thumbnail provided. Further, the developer for ShrinkTheWeb has been trying to contact the addon developer in regards to continuing to offer the service due to the rather large increase in usage. The latter could be one the reasons why the addon is still marked as Developmental.

Tracer is about 27 KB and works with Firefox 1.5-3.0.* (but can be forced to work with 3.1*). You will need an AMO account to download this add-on.

Source: Mozilla Links