Who do you think are some of the funniest contemporary novelists? I like Carl Hiaasen, Elmore Leonard, Donald Westlake Laurance Shames, and authors along those lines.
Terry Pratchett.
And he’s not contemporary, but he’s still funny to me. Jerome K. Jerome.
None contemporary but laugh out loud funny:
Mordecai Richler - The Apprenticeship of Duddy Kravitz, The Incomparable Atuk, Cocksure and many short stories.
Terry Southern - The Magic Christian, Blue Movie.
Tom Sharpe - a South African but very English humour. The first 2 are set in South Africa and got him banned there.
Riotous Assembly, Indecent Exposure, Porterhouse Blue, Blott On the Landscape, Wilt, Ancestral Vices
I also recall I really enjoyed Roth’s The Great american Novel about a baseball team with no home stadium. Has some unforgettable stuff.
Jasper Fforde - The Eyre Affair and it’s sequels.
Thursday Next is, literally, a literary detective and someone is trying to kidnap Jane Eyre out the book and hold her to ransom!
Full of jokes about literature but also laugh out loud funny.
Bill FitzHugh - Pest Control, among others.
A Pest Control Operative mis-describes his business and is mistaken for a hitman; he needs the money, but can his methods work on humans!?
Funniest novel ever – Straight Man, by Richard Russo.
Kurt Vonnegut
I’ll echo Donald Westlake (but you have to be careful what you select, he has some deadly serious writing too – great stuff, but not funny.)
In the mystery vein, you might also try Janet Evanovich’s series about Stephanie Plum, the incompetent bounty hunter. The ninth book in the series just came out, and they’re all laugh-out-loud funny.
Whaddya mean, Terry Pratchett isn’t contemporary?? … and he’s certainly VERY funny.
I find Carl Hiassen repetitive. I mean, OK, I guess all writers are a bit repetititve, but Hiassen seems to always have the same plot and characters.
Dave Berry has two very funny novels out, BIG TROUBLE and TRICKY BUSINESS.
Eric Garcia’s Rex series. Roll on the floor funny.
Piers Anthony before the panties.
Jane Heller esp Female Intelligence
Oh the list could go on and on.
Christopher Buckley
Kinky Friedman (Possibly not to everyone’s taste, but I personally find his novels hilarious.)
I’ll also second the mention of Donald Westlake; especially for his “Dortmunder” series.
I’ll echo Janet Evanovich as the funniest current author. Each of her Stephanie Plum books are laugh-out-loud funny.
In previous threads such as these, I’ve been inspired to try other authors/books and I’ve yet to find someone as consistently funny as Evanovich. For example, a number of Dopers recommended David Sedaris, so I went out and bought two of his books, Naked and Me Talk Pretty One Day. I was severely disappointed. There were probably only three pages total that were truly funny.
What’s this, no one’s mentioned Christopher Moore? And him with a new book just out too, for shame . . .
He’s dead now, but Richard Adams’ The Hitchhikers’ Series was the only stuff that made me laugh my ass off the way it did. Never knew books could do that (though I never knew a book could scare you like Salem’s Lot could.)
That’s Douglass Adams.
John Irving cracks me up. (Hotel New Hampshire, A Prayer For Owen Meany)
My bad; got him mixed up with the Watership Down author. I’ve been going through my bookshelves and it happens. Still hilarious stuff 
Some names not yet mentioned (in alphabetical order yet):
George Baxt has done a long series of funny mysteries based on movie stars, although it started with The Dorothy Parker Murder Case. He went on to do Mae West, Alfred Hitchcock, William Powell and Myrna Loy and a dozen others.
Peter Benchley (yes, the Jaws guy) did two very funny books, Q Clearance, a Washington satire, and the black humorish Rummies, about a drug rehab center. Try him if you like Christopher Buckley.
Carrie Fisher is surprisingly good as a novelist, with Postcards from the Edge probably her funniest.
If you haven’t read Armistead Maupin’s Tales of the City series, you’re in for a treat. It’s infinitely superior to the PBS show made from it.
Ring Lardner and Damon Runyon are classic humorists of the 1920s. A bit dated now, but their styles will always be unique, if much imitated.
Jane Smiley’s Moo is an academic satire that you don’t need to know anything about academics to laugh about. David Lodge is the British equivalent, but more on the academic side.
Gore Vidal can’t be missed in a discussion of humor. His darkest satire is probably Live from Golgotha, one of those books meant to offend everybody.
Dex, boobah said that Jerome K. Jerome, not Terry Pratchett is the non-contemporary one. Connie Willis’ To Say Nothing of the Dog is a modern take-off of Jerome.
And how can you mention the wonderful Terry Southern and not mention that he co-wrote Candy?
I’ll third Evanovich. There’s a scene in her Christmas novel with Stephanie Plum, Lola, and a dwarf on the hood of her car that made me laugh so hard I started hyperventilating. Don’t read her romances, though! I just read Full House and it was really bad.
Pratchett is very funny. Vonnegut, Henry Fielding, Jane Austen–all funny.
Tamar Myers’s mystery series with the Mennonite herione makes me laugh. I seem to recall Joan Hess’s Maggody series being at least amusing. Sharyn McCrumb’s book set at a sci-fi convention (Bimbos of the Death Star, or something similar, and I think there’s a sequel) was very funny.
I’ve only read the first three Spenser novels, but each was at least amusing. No idea if the later novels are still funny.
There was an absolutely hysterical mystery called Date with a Dead Doctor, by Toni Brill. There’s a sequel I’ve never read.
Mary Kittredge wrote some funny books, as well, also mysteries.
Julie
Barry Hughart’s Master Li and Number Ten Ox novels are extremely funny, particularly the first one, Bridge of Birds.
Neil Stepheson’s Cryptonomicon is hilarious, and an excellent read. It’s probably the best book I’ve read in at least a year.
The funniest book I ever read (four times) was The Milagro Beanfield War by John Nichols. His follow-up books in the trilogy weren’t nearly as good.
Disappointed by Sedaris? Really? I love his stuff. I laughed so loudly through “Naked” that I annoyed my SO. Proof that YMMV is a truism.