A Terry Pratchett Fan! I knew there was something I liked about you, Del!
Joe R. Lansdale is a great storyteller, and would be really good as an audible book. He has some great short stories ("Incident on and off a Mountain Road" is one of my favorite scary short stories) and his Hap & Leonard series is also really good--not sure how you'd classify the series--buddy book/thriller?
Reading Donald Harstad right now, but he only has about 5 books--don't know if they're available as audio books. Police thrillers set in small town Iowa.
Christopher Moore was excellent for his first several books, but starting with Fluke they really went downhill IMO. First 5 or so are great.
Another vote for Jim Butcher's Harry Dresden series. (And on a side note, if you own the first "Codex Alera" book in hard cover sitting around gathering dust, they've become collectable and you can sell them for $$.)
Tanya Huff is a great deal of fun, in spite of the fact that the Lifetime channel tried to destroy her "Blood" series (watched a few minutes of one episode, and stopped in disgust.) "Summon the Keeper" is good fantasy with a big dose of humor. "Stealing Magic" is a compilation of short stories, many of which feature Magdelene, the world's most powerful (and laziest) wizard, who likes sleeping, eating, drinking, and handsome men. Not necessarily in that order.
Neil Gaiman. Carl Hiaasen, although he might not be as funny if you've never lived in Florida ("Lucky You" is a good one.) Bill Fitzhugh (try "Pest Control".) Asimov is fabulous. Anne Bishop's "Tir Alainn" trilogy. (Her "Black Jewels" trilogy is also good, but if you read it stop after the first 3--follow-ons are dreck.) Spider Robinson's "Callahan" series. Patricia Briggs, Faith Hunter for Urban Fantasy.
If you don't mind books targeting young adults and being fairly predictable, there's a new author--Marissa Meyer--doing a pretty good (so far) 4-part series loosely framed on fairy tales. The first one is "Cinder"--only Cinderella is a cyborg. 3rd book in the series is coming out soon.
And one chick-lit, just because it's good for you--try Jennifer Crusie/Bob Meyer's "Agnes and the Hit Man."