A quick way to find out what’s trending on Twitter and why can be found at WhatTheTrend. Get last week’s Twitter trends, the Year in Review and also topics trending around the world. Definitions of hashtags and explanations of why something is trending are provided by users. A tool for

Find out what percentage of traffic on Twitter contains a particular hashtag on hashtag.org. You get a graph for the past week which includes daily and hourly numbers. Clicking on the graph will get you 30 day data and if you sign in (free registration) you will also be able