Flash cookies, aka "super cookies," can be used to track your browsing just like normal browser cookies. But Flash cookies will stick around even if you delete your regular browser cookies, and they can't normally be viewed.
The FlashCookiesView tool shines a light on these out-of-the-way files. The super cookies, known technically as local shared objects or LSOs, do have legit uses, such as saving your preferences for watching Flash videos on a particular site.
But online marketers discovered that the cookies can also be used to effectively track you from site to site. The small files sit tucked away in a Documents and Settings folder, and can't normally be read clearly because they're in binary format. For more details on super cookies and how to foil them, see "Are Flash Cookies Devouring Your Privacy?"
FlashCookiesView lists all your LSOs with details including the associated URL, filename and creation date. A bottom pane lists the cookie's contents, which might include a unique userID for tracking. You can quickly delete the discovered files, or save their information to a text file. Techie users can also see a hex dump of the raw data within the cookie.
The simple FlashCookiesView is a worthwhile tool for learning more about a sneaky tracking technique, and it doesn't require installation. Just unzip the download and double-click the executable. For a similar and useful tool, see the BetterPrivacy Firefox add-on, which can automatically delete your Flash cookies when you open or close your Firefox browser.