The "Failure Feedback Forum" on this website can be used to report bugs.
e4Graph - by Jacob Levy, implements storage for graph-structured data (a superset of tree-structured) on top of Metakit.
KitView - by Steve Landers, was a project to bring generic database editing and data dictionary capabilities to Metakit.
MkSQL II - by Gordon McMillan, is an amazing SQL engine in Python, on top of the Mk4py binding he also created.
KitViewer - by Brian Kelley, is a Python/wxPython-based portable version of the Win32 app I hacked up a long while back to browse MK datafiles (comes with Win32 installer, other platforms require somewhat more work).
Metaserve - by Brian Kelley, is a Python client/server setup for Metakit. Client requests are transparently "remoted" to a server. On the client, it all looks like ordinary views.
dgMKViewer - by Detlef Groth is an elaborate Metakit viewer and editor in Tcl, which also provides access to the Oomk wrapper.
Metakit@Web - by Stefan Vogel is a Tcl script which runs under the Tclhttpd web server to create a nice manager to list, browse, create, and edit MK datafiles.
Python Desktop Server - by Georg Bauer is a weblog construction kit, a news aggregator, and quite a bit more.