PPC Software & Tracking Software
Pay per click marketing requires you to pay for each click so it is important that you properly target your ads and track and measure each click.
Google AdWords and Overture include their own pay per click tracking software inside their pay per click products. Many marketers (especially large ones) are not interested in sending their conversion data back to the search engines though.
Overture recently created a premium tracking service (by the name of Overture Search Optimizer) and has many approved third party bid management software vendors which can help you improve your ROI or profit by controlling your PPC accounts at the price per action level vice price per click level.
Rank Checking Software
I do not use rank checking software frequently other than to monitor changes in search engine algorithms by monitoring many different sites in different industries. There are a few free, quick, and interesting ranking tools I recommend and enjoy using.