TortoiseDarcs is a GUI frontend for darcs, modified from TortoiseCVS. It is Windows-only, and integrates with explorer to colour files depending on their status, and to provide a contextual menu for doing darcs operations.
Some screenshots (some large images)
TortoiseDarcs can be downloaded from its Sourceforge download page. The installer is TortoiseCVS.exe, which contains everything you need. TortoiseDarcs-no-_darcs.zip contains the source, with binaries for all the libraries needed (mostly wxWindows). _darcs.zip is an archive of the darcs repository for the project, without either current or pristine included. It's ridiculously large mostly because it has the darcs binary under version control (You can recover the entire repository by running darcs repair and darcs revert -a).
After installation, files inside a darcs repository will be marked - green if there are no unrecorded changes, orange/red if there are unrecorded changes, and grey if the file is not in the repository. The overlay can be changed in the preferences.
Darcs commands are provided via a contextual menu in Explorer. Some are put directly into the menu, and others are in the "Tortoise" submenu. The commands will act on either the item(s) selected or, if no item is selected, the containing folder. A command will only appear in the menu if it makes sense for that command to act on the current item.
It hasn't been made pretty for release, but we have been using it internally for some months now, and we thought other people might be interested. Not everything that darcs can do is available, the feature set being largely determined by our needs. In particular, there is no support for Send/Apply or pulling from http. The code is also rather messy, and was taken by modifying a version of TortoiseCVS taken from its CVS head branch in early November. Although the installer asks about the language, only English has been done for the darcs stuff. It comes with a darcs binary, which is the current (as of 2006-11-23) darcs-unstable. It also contains binaries of KDiff3 and the PuTTY utilities.