If you are a regular user of Google you'll probably want to take the Google Toolbar for a spin. The Google Toolbar gives you access to all the power on the Google search engine in your IE tool bar. The Google Toolbar allows you to run a site search, limiting the search to just the site you are looking at. Their PageRank allows you to know how popular the page you are looking at is. But, the feature that I find most useful when doing research is the Unavailable Page Snapshot. This option allows you to see a snapshot of the current page as it looked when Google last crawled it.