The most widely used and reliable tool for monitoring the web pages for plagiarism. It checks for the uniqueness and content originality.  

 A small and lightweight tool to compare the two web pages for finding duplicate content. Gives a good snapshot of similarity details between two given URLs.

A web based tool for finding the duplicate content within your website. If your site is particularly big and wish to find any duplicate content then duplicate check is the one for you. 

Know how much of your web page is spiced with content and how much with the code. This tool from SEO chat aims at giving you the ratio of how well the balance in maintained in your pages.

Although currently keyword density might not weigh much in search engine ranking factors but a certain degree of keyword balance may be required. Use this tool from SEO chat to measures the number of occurrences and get the percentage of your targeted keyword.