I actually was just at a small meetup for people in the SF Bay Area who are building memex's. The Zettelkasten was a common theme in several of the projects people were working on. Here are my notes from the event for anyone interested: http://ceasarbautista.com/posts/memex_meetup_2.html

There are a couple projects that came up that were loosely based on the Zettelkasten:

- IdeaFlow by Jacob Cole - Roam Research by Conor White-Sullivan - "Cards" by Joel Solymosi

IdeaFlow and Roam are both basically WorkFlowly except that you can link bullets together, plus additional unique features. The ability to link bullets together basically makes it a Zettelkasten, and enables many cool features. As Conor puts it "You shouldn’t have to know the structure of your thought as you’re typing".

Cards was more faithful to the Zettelkasten in that the metaphor was index cards instead of bullets. The unique thing about Joel's approach is that you can transclude them into documents (sequences of cards), which was a feature inspired by Project Xanadu. That enables Joel to reuse cards across many documents, and had the benefit of letting him effectively update multiple documents at once by editing a single card.

I've been writing an encyclopedia for the last six years. When I heard the Zettelkasten idea it made me wish I had heard of it earlier. It seems like a potentially better way to organize information since the links are between paragraphs rather than pages.