I apologise for adding to everyone's mailbox, but I noticed that this list is twenty years old today - on 21/2/1997 I initialised the list, which was then hosted at Mathworks, and run by majordomo. The 20th anniversary of the first post (which wasn't mine!) will be 5/3/2017 (that is, in about two weeks), but I won't be saying all this again.
Many thanks to everyone who has shared so generously of their time and expertise over the years, helping other people on this list, and to Mathworks, who hosted it for most of the last two decades. Bonus thanks to Kendall Libby, who has co-moderated this list with me since the move to teaparty.net (and mailman).