Vodo-Siosk Baas set up a Jedi enclave there to train Jedi. Over the years, several trainees at this enclave became Sith Lords, but that probably wasn't Dantooine's fault. Darth Malak went ahead and destroyed the enclave, occupied the planet and executed pretty much everybody. He was not the most popular ruler Dantooine ever had.
The Rebel Alliance had a secret base there. Many of the top military leaders were stationed at the base, and it was where most of the Rebel research and development activity occurred prior to the Battle of Yavin. The base was frequently over budget, and was eventually closed by Mon Mothma.
Malak and Revan both trained on Dantooine, as did Exar Kun. Vandar Tokare was one of the Jedi who ran the place. Darth Felchus was born on Dantooine. When the Rebel base was there, it housed such greats as Jan Dodonna, Walex Blissex, Vanden Willard, and Tigran Jamiro.