If you like classic mysterys of a more off-beat nature you should check out Ramble House press. They always make the 1st chapter available free and, though it's not posted on the Web site, they sell pdfs for $5 a shot. I've been reading their William Masterman reprints, which are sort of on the border between horror and mystery fiction. I'd also recommend Gelett Burgess (although most of his books are available free on Google books), Joel Townsley Rogers, & Hake Talbot.
Here's their Web site
http://www.ramblehouse.com/
Max