There are numerous tools for checking your page rank you can download any one from the list.SEO Book Rank Checker Plugin SEOmoz PRO Campaign Raven Tools Microsite Masters Sistrix Search Metrics SEO Serp Chrome Extention
Keyword search and page ranking is only half the job. YOU NEED to be able to see back links not just from clients/your site but competitors !! Aim of the game is to be top, and you cant do that if you dont know whose above you and where they are. Why try to find places to link when the right tool can do that for you too??? Sorry if I sort of opened the question up a little, but if one is going to pay for something we all want ROI and the more detailed information we get for our investment, the better the benefit. Tools should not cost money, they should MAKE MONEY !!
Google toolbar is the best tool for checking Pr of any website, or you can manually ranking for a particular keywords in search engine. Many other tools which you can search on google.