Everyone's familiar with tag clouds, but Aaron Bassett put a slight twist to the now commonplace clouds. Aaron calls them Focus Clouds. Basically, they're still tag clouds, but instead of weighting tags by number of times used, there's some weight given to how recent a tag is. There's also some simple highlighting going on with related tags.
The idea is that the focus cloud then gives you an idea of what is currently of interest. Aaron's code is available on his blog. The code is a bit buggy, but interesting nevertheless.