Continuing the discussion from Serge Recommendations?:
It seems that there are quite a few fans of Andrew's NLC modules.
They're easy builds using common parts, yet have unusual functionality (even for Eurorack). His most popular module seems to be the Sloth series. They are slow, all-analog chaos generators with three levels of speed (Regular, Super, and Stasis).
I'm particularly a fan of DelayNoMore, two PT2399 lo-fi delay chips tied together with four feedback paths. Most PT2399-based modules pose as echo effects, but this fully embraces the junk quality of the chips with a special emphasis on their failure states.
In the US, his PCBs and panels are carried by ModularAddict and Synthcube. Thonk has a fairly large line-up for Europe. Otherwise, you can order directly from him.