We've talked about the concept of PageRank before - the numerical measure that Google assigns for how important a given page is in the context of the overall web. PageRank is a critical determining factor in how search results are ranked by Google, and therefore a critical component of SEO.
We know how important PageRank is, but how do we know what PageRank is assigned to a given web page? There are a number of tools out there, but one that I find to be useful and convenient is the Google search toolbar. Not only can you easily search from the toolbar, but, among other things, it also shows you what the PageRank is for the page you're currently on.
This is a great way to quickly estimate how valuable a link is that you're receiving by knowing how reputable Google thinks a given page is. That said, pagerank in the toolbar is not always the most up-to-date, and it also doesn't speak to how relevant a specific page might be for a given topic (a page might have a lot of authority but only for a single topic and that might be understated in the single measure of PageRank).
Hope you can add Google Toolbar to your SEO toolbox as yet another valuable SEO tool that makes your analysis quick and effective.