darcs is one of many version control systems vying to succeed CVS. Specifically, darcs belongs to the class of distributed version control systems and is thus naturally superior to Subversion with its centralist approach (at least if you want to manage a distributed project and can't just get by with the central repository). Normally I wouldn't say much about something like this — after all, there are currently more version control projects than there were editors in the 80s. But seriously now: who can ignore a version control system that is written in a functional programming language with lazy evaluation (yes, exactly, this thing is in Haskell — so much for the claim that Haskell is unsuitable for practical projects) and describes itself as being based on a "theory of patches" with roots in quantum mechanics? And the programmers even use literate programming — yes, that somewhat forgotten method by Knuth of combining documentation and code in a single source file and developing a program from a documentation-centric perspective. Simply cool.