The Data Visualisation Catalogue - Reference tool for data visualisation
Site Rank Data - View historical rank information of websites via time series charts.
Flourish - Powerful, beautiful, easy data visualisation
Q-Stats - Get free marketing insights for every question on Quora.
CodeAnalogies - Visual explanations of web development topics
Seoxan - check seo report for any website, alexa ranking, server information, meta tags, authority, page speed and more