Pretty Maids all in a Row was a novel written by Chris Golden, the premise was that the vampires Spike and Drusilla were on a mission to kill not only the Slayers-in-Training but also the Slayer. We met many SIT's in this novel and they are listed under Past Slayer's in Training.

Curent Slayer's in Training

Kennedy - American, the older of the bunch. Hardworking, trained by a Watcher, responsible. She is also currently romantically involved with the current Slayer's best friend Willow Rosenberg.
Molly - British, confused. She tries hard to live up to Kennedy's expectations.
Rona - American, Rona had no idea what a slayer was until the massacre on SIT's began. She was found and taken out of her home and is now realizing her destiny.
Vi - Cowardly, quiet, a bit stuffy, but she trains and tries hard.
Amanda - American, a resident of Sunnydale, California. She took immediately to her calling, which was discovered by the slayer's sister Dawn. She managed to fight alongside the current slayer and hold her own.

Past Slayer's in Training

Kate Huchins and her Watcher from Liverpool, England were killed by Spike and Drusilla on May 22nd, 1940.
13 year old Collette Boisvert of Nice, France was taken from her family at an early age to be trained by her Watcher Arno. She was an avid fencer, an enjoyed the novel the Three Musketeers. She and her Watcher were killed by Spike and Dru on June 2nd, 1940.
On June 12th, 1940, Alessandra Cavallaro was hung from the doors of St. Michael's Cathedral in Venice, Italy to die.
On June 15th, 1940 11 year old Marya Bajdek of Warsaw, Poland was killed by the vamps. Her Watcher Jozeff Strakus tried to save her and failed.
On June 22nd, 1940 an unnamed SIT from Benghazi, Libya was drained by the vamps as her Egyptian Watcher watched helplessly. He was then bound to the desert floor by posts and left to die. He did survive though.
In Boston, Mass. on July 6th, 1940 Rita Gnecco answered the door and unknowingly let Spike and Dru in. They killed her parents Giovanni and Teresa and turned her Watcher Arthur Cabot. Arthur chased her down into a church and he killed her as the vamps watched.
Ariana de la Croix from Geneva, Switzerland had been training with her Watcher Charles Rochemont for 9 months when the attacks on the SIT's began. She became friends with the current slayer of the time Sophie Cartensen, and fought alongside the slayers Isabel Cortez and Eleanor Boudreau during the Council's battle against the Ice Demon Skrymir. She was not chosen to be the Slayer and instead became a Watcher.
In Mykonos, Greece the SIT Valerie Vourtsas and her Watcher Donald Morgan were killed on August 18th, 1940.
There is mention also of SIT's in Prague as well as Hong Kong.