Part of me wants to be picky and say that Glory Road is a high fantasy novel, not SF. That part, obviously, is currently in command of my fingers.
A Song for Arbonne*, maybe, but The Summer Tree is really good.
Without a doubt. I can’t really separate it from its sequels, however - mainly as it’s been a while since I read them.
As a whole the trilogy is very good and well worth reading. It just goes from excellent (1st book) to average/poor (3rd book). Because the 1st is so good you have to read the rest.
But the later novels that I mentioned are among my absolute favourites.
Quoth Der Trihs:
I hadn’t heard of that one… Is it any good? The first two Bahzell novels were great, but the third seemed to be suffering from a bad case of lack-of-editor-itis.
Back on the OP, Zelazny’s Amber series starts with a character presumably from our world being swept up into a cross-world intrigue. But it turns out that he was from the other world to begin with, so I’m not sure if it counts.
Zelazny also had a great short story, “Unicorn Variations”, with the premise that every time an Earthly species goes extinct, a species from the fantasy world can cross over. Unicorns are waiting for humans to kill ourselves off, to make room for them. A backpacker in the Pacific Northwest, coached by a sasquach, must play chess against a unicorn to decide the fate of the species.
And while we’re on the topic, whatever happened to Skald the Rhymer’s novel along these lines, that he was always asking for advice on? Did it ever get published, then?
James Tiptree Jr.'s Up the Walls of the World is a good one. You get a two-for-one: a group of aliens on their homeworld and a group of humans switch minds.
I finished it and decided that I hated the middle third third, so I threw out that part and started over. Changes made during the middle third necessitated throwing out the final third. I am now about one month away from finishing the final third.
I thought it was pretty good. But then I liked the third one, so YMMV. It’s available bundled in with new editions of Oath of Swords, and in the Weber short story collection Worlds of Weber.
Oath of Swords by David Weber is available as a free ebook on the Baen Books site.
The Seventh Sword Trilogy by Dave Duncan.
Den, in the Heavy Metal movie and magazines. Teenager lifted to body of barbarian swordsman.
To take things to their most extreme, in Philip José Farmer’s Riverworld series, everyone who has ever lived (including Neanderthals and at least one other human species) wakes up one morning on the banks of the River.
I just skimmed this whole thread to see if anyone had mentioned that yet 
I adore that trilogy, which I pimp on every possible opportunity, and nobody ever seems to have heard of (actually, make that Dave Duncan in general - I like his other stuff too)
I used to have a fantasy principle - never read anything with the word “Sword” in the title - they’re all derivative crap. This is the series which changed my mind.
Among other sterling qualities:
- He has a great turn for inventing memorable proverbs (“The well is calling the puddle deep”. “You can’t have omelette and roast goose”) which adds a terrifically realistic flavour to his invented worlds
*Wonderful subtle skewering of that prize dick Thomas Covenant and his incessant meanderings of whether the world he found himself in was really real or not. That question is disposed of very thouroghly by about chapter 3.
*Completely eschews the Standard European Medieval Setting common to so many hack fantasy writers in favour of a far more original Hindu/Eastern flavour of world
*The Great Important Quest (when you finally figure it out) is actually great and important. No McGuffins like “rings of power” or any of those tired cliches. And, yes, the gods really did have to bring in an outsider from another world, and nobody from that culture could have done what he did. You get to the end and it actually all makes sense.
(yeah, I like those books. Can you tell?)
A lot of H. Beam Piper’s stuff deals with alternate universes and what happens when they meet; the best two stories of his along these lines are “He Walked Around The Horses”, which provides an interesting explanation for a real-life disappearance of an English diplomatic courier in 1809, and the other one is Gunpowder God, also published in slightly expanded form as Lord Kalvan of Otherwhen.
In Gunpowder God, A Pennsylvania State Trooper ends up accidentally transported across time to a less advanced (early Renaissance-esque) North America where the secret of Gunpowder manufacture is closely guarded by a Religious Order. The protagonist happens to be a firearms enthusiast and knows how to make gunpowder, flintlock mechanisms, and rifled barrels and, as you can imagine, he very quickly uses this to his advantage. It’s a good story, and is available in the Ace Science Fiction collection The Complete Paratime, which is an excellent collection and definitely worth a read, IMHO.
Its the book telling me, right here on the cover, how can I argue with the book. 
Hominids by Robert Sawyer. But it’s the Neanderthal that is transported to our earth, assuming we are talking about the same book. A pretty good read, I recommend it!
I finished it. Then I decided I hated the middle third, so I threw out all those chapters and started over; then I realized the changes made in the middle third made the latter third stupid, so I rewrote those too. Or, rather, am rewriting. By my current schedule I will be done with it on 29 April.
Darn it, this is getting expensive. (amazon, amazon, amazon… you know, if Ed wanted money…)
Do metaphysical realms count? I’m sure there are a few PK Dick books/short stories in there that cover those grounds, Ubik for one.
Star Trek has had a few episodes like this, of the Captain vs Alien type.
More Heinlein!
Farmer in the Sky
Tunnel in the Sky
Farnham’s Freehold (time travel)
Job: A Comedy of Justice
The short story “The Silver Key”, by H.P. Lovecraft.
Harry Turtledove did several books in a series about a group of Roman soldiers (and one Celt, I believe) that have them sucked through a vortex and onto an unfamiliar world – I think the first title was “Legion of Videssos”, maybe. The leader gets involved in local politics and women. It was an okay series – I’m not sure I even ever had all of them