You would find many tools on internet that can give you your websites ranking for given keyword on Google, Yahoo and MSN. Some of them are free and some are paid service.
'Search Engine Position Checker' is a free tool with which you can check your website's position on 12 search engines. Goole, Yahoo, MSN, AOL, ASK and AltaVista (+ UK version of these search engines).
This tool checks website ranking in real-time for all these search engines. It even checks for any sub-domains. You can do as many searches as you feel like. Did I tell you its absolutely free :).