http://www.digitalpoint.com/tools/keywords/

Tracking your targeted keyword rankings historically for major search engines like Google, Yahoo and MSN becomes easy with this tool from digital point solutions.

In order to use this tool, you just need to create one account by registering with the site which is absolutely free. This registration also requires a Google API key. By default it will have automatic configuration settings for google, but for yahoo and msn you need to install one script on your web server which is provided by them.

Once you have your account ready you can monitor keywords for your each optimized page. Besides ranking position it also records the daily, weekly and monthly change frequency in your keyword ranking fluctuations. This can be of very useful information considering your competitors activity who are optimizing for similar keywords. The ups and downs are clearly marked with + and - signs so that you can focus your next steps on improving those rankings. Multiple keywords, ranking for a common URL can also be tracked with this tool.

On the left side of keywords if you click the graph icon it will show how your optimized keyword has performed over a period of time. These recordings will serve as a valuable input for your next optimization plans. To watch your competitors search results URL which are around your targeted keyword go to edit preferences and set 'show surrounding URLs on manual query' to yes.

Added to above features it can also track the back links, page rank and create custom charts for you.