The most prominent, at least in my Internet circles, is Corona-Chan: Spreading the Love, an anthology assembled in just a few days by David V. Stewart and many, many authors of the Pulp Revolution. I've talked about some of them on this blog before - Jon Mollison, for example, has donated his entire novel Adventure Constant, which I reviewed a few years ago and still recommend wholeheartedly. Other contributors include Justified's Jon Del Arroz and former and current Geek Gab hosts Brian Niemeier and Daddy Warpig. They are joined by a host of other independent authors, many of which have appeared in various issues of Cirsova magazine. And speaking of Geek Gab, their most recent episode has as guests contributors John Daker and Yakov Merkin:
If you prefer something a little more mainstream, gonzo techno-thriller writer Jeremy Robinson is offering a five-book package on his website, with a sixth offered for joining his mailing list. Now, I haven't read a great deal of Robinson, but what I have has kept me interested. Of the books in his bundle, I'm particularly interested in Flux, which sounds like it shares some premises with Eric Flint's Time Spike or 1632. The latter of these also happens to be free, from Amazon or Baen Books directly, although it's been so since long before the Wuhan Flu made its presence known. Come to think of it, the Baen Free Library is another great source in general for free things to read, including one of my perennial favorites - Larry Correia's Monster Hunter International.
To conclude, I'd like to thank all the authors mentioned above for their generosity in making their work available to the reading public during this crisis. Now let's do our part by keeping our hands clean and giving the coronavirus no chance to spread.