Well, I've got partial sound working in blockade.c. Definitely better than silence!
I'm trying to come up with some simple way to deal with the aliasing distortion you get from generating high-frequency square waves the "simple way". This is really apparent in Minesweeper.
For the mathematically inclined, the problem is described and completely solved by the approach in this paper:
However, it's a pretty heavy-duty approach - probably too unwieldy for MAME.
I'm also getting ready to move to a blog based on Movable Type. I really want "categories", so that I can blog about anything and not alienate the people only interested in MAME. :) I grabbed avoidspikes.com and I hope to set up shop there within a week or so. I'm going to move my dsplib.com content there as well.