I've been using xfig (on and off) since the early 1990s. It's an old-school X-windows program for drawing vector graphics. I'm not sure how many people still use it, but I find it easy to generate simple "publication-quality" graphics - the crudeness of my figures reflects the craftsman, not the tool :-)
Xfig comes with a set of libraries, including electronic symbols, but I don't care for them. You may feel the same about these, but you are welcome to use them if you like. The symbols above can be downloaded here.
To generate a PNG diagram for inclusion on hackaday.io, I draw the figure, then export as a PDF file. The make_hadio_figure.sh shell script discussed in the other log can then be run to make a white-on-black PNG file.
I think I have a few other component symbols floating around that didn't make it into this "library". I'll add them and update the file as they turn up (or as more are generated).
I'm starting to use the new, simpler MOSFET symbols like those in the 3rd edition of The Art of Electronics.