- Reddit: Most similar. Similar types of posts, but with a slightly different user base and layout (some would say much uglier).
- Stumbleupon: Easy to waste time, but is harder to find what you want. Forces you to view many pages you wouldn't really be interested in.
- Pikk: Not sure about this one. Seems relatively new and unestablished
- Slashdot: Tech news, but only a few articles a day.
- Alexa: Internet statistics site. Can show you recently hot topics.
- OldDogg
- NewPolitik Political news, somewhat like digg.
- Fark
- Thuhm
- MetaFilter