http://www.tinykeywordtracker.com/ 
Free and Paid
Features:
- Checks and updates the keyword position on daily basis.
- Shows the differences in position by comparing it with last checked position.
- Displays a graph to show how a keyword has performed over a period of time.
- Provides automatic alerts to give updates on rankings.
- Support for reporting in Excel and CSV format.
- Support for unlimited number of keywords and website.
- Alerts and automatic reporting capability.
- Scans 10 to 200 Google search result pages.