I love lemmy.sdf.org the best - it's a unixy ragtag underdog cyberpunk kind of place running on a pubnix cluster, whose frequent downtime only adds to its charm. Three-character dot-org domain name (aura). Broad spectrum of users, unified by finding something like a pubnix cluster cool.

Usually the downtime lasts a day or two at most, the plucky pubnix admins get it back online and we celebrate. But it's been down for over a month now :(