Becoming the Hawk by D'nalia
Buffy the Vampire Slayer and Mercedes Lackey Mage Winds Trilogy.
Xander while saving the world is transported to another world

Gate, Rebirth and Restoration Saga by Snowcrash
Angel, Buffy the Vampire Slayer and Mercedes Lackey's Valdemar Universe
Some people find new lives and happiness.

Of Chainsaws and Shotguns by Danii
Buffy the Vampire Slayer & Evil Dead/Army of Darkness
Ash moves to Sunnydale and find out that it isn't as friendly and danger-free as he though it was.

The Price They Paid by Voracity
Buffy the Vampire Slayer and Mercedes Lackey's Jinx High
Giles leaves on vacation and things start to go to Hell, literally for one person.

Vision of Darkness by Pixiestyx
Buffy the Vampire Slayer & Hercules/Xena