I can't remember the last time I've seen a tag cloud. As a UX designer, I recommend against them since they're not typically useful to users. Well-organized navigation and on-site search tools are usually effective. But maybe on an educational site like yours, where there's emphasis on learning and discovering, listing everything might actually be a good thing.
Also, thank you for using the correct Twitter logo. One of my biggest personal pet peeves of mine is the bubbly "t" logo!