Let me see, I'm a huge fan of Jack Matthews whom I interviewed a few years ago. http://www.ghostlypopulations.com/20...jack-matthews/
He's published a lot of short stories and novels, all are wonderful. I'm writing a book about him and helping him to convert his out-of-print titles to ebook. His how-to book on writing (which I helped him to publish) is great http://www.barnesandnoble.com/w/work...ews/1100572933
and in fact, in about a week, I'll post on MR how to download a free DRM-free way to download this guide. (If you don't check MR often, send me an email idiotprogrammer at gmail.com and I'll let you know when I post the announcement).
Lately, I've been a fan of Christopher Morley, definitely an underappreciated author. http://www.gutenberg.org/ebooks/sear...r_id&query=109
Haunted Bookshelf which I'm now reading is great (and free).. His best stuff is not public domain yet though.
Also, John Kendrick Bangs, a witty 19th century metafictional author http://www.gutenberg.org/ebooks/sear...r_id&query=979