Swarm shows concentric circle thumbnails of the most popular wensites of the moment. As sites become less popular they slide outwards.
Swarm uses a firefox plugin to send anonymous info back to a central server, so this is only a list of what’s popular with those that use that plugin not the entire net. This is NSFW as you might expect, some of the most popular sites are XXX in content. What amazed me was the low quality of that XXX.
Link Via Digg.com