Of the top 100 sites on the Web, which ones grew the fastest in 2008? In a report it is preparing to release tomorrow, The comScore 2008 Digital Year In Review (which you can sign up for here), comScore ranks the 20 fastest-growing Web properties. These are out of the largest 100 sites overall. They are shown below, as measured by growth in unique visitors. (Interestingly, in a separate…