6pli (still in alfa version) lets you navigate a set of del.icio.us tags in a dynamic network environment. The interactive tool produced on flash delivers a fascinating output with different visualization methods such as elastic net 3D, elastic net 2D and circles 2D.
6pli is still in alfa version and there's only a few del.icio.us pages that you can explore, but soon it will probably open to anyone who might be willing to see their del.icio.us account visualized in this fashion. Even now, you can have your account displayed by becoming a 6pli alpha-tester. All you need to do is send an email to firstname.lastname@example.org.