Google Toolbar

You need to download the Google Toolbar. It has a lot of features that you may or may not use but the biggest advantage is it allows you to see Pagerank™ at a glance. Yes there are other place you can get page rank without the Google Toolbar and places you can estimate your future Pagerank but the toolbar is pretty handy.

Pagerank is not the be all end all to webranking it was in years past. In fact a great many experts believe there is a public PR published to the toolbar, and internal PR that is not published, and it's the internal PR that really plays a bigger role in rankings.

There is also a body of people who believe the toolbar is used by Google to gather data about you. Conspiracy theories abound with reasoning like they use it to monitor click thrus and improve rankings to it being used to ferret out spammers. So if you're running high risk SEO tactics you probably shouldn't use the toolbar on a regular basis just to be on the safe side.