A search engine rank checker will tell you how your website ranks in one or more search engines. It also helps to know what the search engines think of your site although you may need to guess at methods to improve your ranking.
I typed "search engine rank checker" into Google and the following sites were listed. For each one which was free, I used the url of a well known keyword research tool and the keyword "keyword research software". This is what I found:
Number one listing was sitereportcard.com. Here you can insert four urls and one or more keywords to find the ranking. The idea is that you insert your own page address and three other sites with which to compare it. Rankings are returned for Google, Yahoo and MSN (now Bing). It returned my url as not in the top 100 for Google and Bing but number 19 in Yahoo.
Number two listing was SEOcentro.com. You put in one domain and a competitor if you wish plus your keyword. This returned my url as number 1 in Google, number 24 in Yahoo and not ranked in Bing.
Googlerankings.com was the third of my search results. The problem with this is that unless you already have a Google SOAP API key, you can't use the tool. No, they won't issue any more APIs and no, they won't help you if you've lost the one you already had.
Fourth was iwebtool.com. Again, you insert the url and keyword. There are drop down menus for Search on (search engine) and Limit search to (a number of results) but each menu only offered one choice - Google and 100 results. This too listed my url as number 1 on Google.
Fifth was marketleap.com. A "problem" was returned for this one.
Next at six was web-inspect.com. This one couldn't find my chosen url at all in Google, Yahoo, MSN, Hot Bot or Teoma.
Seventh was ineedhits.com. To use this tool I needed to create an account and having done so, I was asked to put a button on my website. Results were: Google - higher than 100, Yahoo - number 25 and Bing - number 50.
Next, at number eight came linkassistant.com. Rank Tracker is part of SEO Power Suite which you can download free or paid. I already had this thanks to my hosting account so I plugged in my url and it returned number 1 on Google and number 25 on both Yahoo and Bing. I really like this tool; it creates a project for you and you can do all sorts of things with it - too many to mention here as it's worthy of an article on its own.
Number nine returned the FAQ page at digitalpoint.com - tools. I finally discovered that I had to register here too so I didn't bother.
Finally at ten, Rank Checker from SEObook.com. This is a free download for which you have to register. As far as I can tell, it is only available for Firefox. It's very easy to use; just click on the logo on your status bar in Firefox, insert the url and as many keywords as you like and there you are. Results can be downloaded in CSV format. My url was #1 on Google, #19 on Yahoo and #25 on Bing.
So my picks for a search engine rank checker based on these results would either be Rank Tracker (no. 8) and Rank Checker (no. 10) which returned more or less the same results.