WordCounter.net - Count words, sentences, paragraphs etc.
Word Counter - A simple, beautiful word and character counter
Heytools - JavaScript tools, AJAX tools and some fully server side tools.
Word Count Tools - The must-have free word counter that provides an extensive report about the word count, character count, keyword density, readability & many other useful stats.
KeywordDensityReport.com - Website Keyword Density Reports
Count Wordsworth - Count Wordsworth makes it easy for you to monitor your literature-related metrics online.