Advanced Rank Checker lets you check your ranking on the keywords you provide to the system. You can check your keywords ranking once a day.
Keep track of your Google rankings. See your current and past rankings for the keywords you track inside your WordPress admin panel.
This plugin will track your Google Search Engine ranking for keywords which bring visitors to your website.
The Whoosh Traffic plugin provides a Rank Tracker and a Keyword Research plugin integrated right into your blog.
Google Rank Checker - SEO Tool with Google API provides the estimated Google position for a keyword and corresponding URL.