From Mefi Wiki
See also Mefi Clones: sites using software very similar to the MetaFilter front-end.
Plenty of other sites exist which are similar to MeFi, but with different engines or purposes. These include (but are not limited to):
- Barbelith - political self-organisation.
- Fark - quick and dirty links and discussion.
- Kuro5hin - focused around longer articles.
-  - "massive link propagation" section
- Memepool - short, link-heavy articles with no discussion.
- Plastic - more news and politics than links. One of the editors now is ExMeFite holgate, aka Nick Sweeney.
- Slashdot - news for nerds. Inhabited by many a troll.
- Devoter.com - community weblog covering politics.
Still more: Open Directory: Collaborative Weblogs