Think I've got this right:
-The Time Lords were one of the oldest races in the universe whose society was transformed by the work of three individuals; Rassilon, Omega and The Other. Rassilon was a legendary philosopher, Omega the scientist who perfected the Black Hole technology that would ultimately power the Time Lords' society and The Other was a unique figure, a scientist and artist who was at least the intellectual equal of the other two. There have been clear implications at several points in the show's history (And interestingly at least one flat denial) that the Doctor is a reincarnation of The Other. For example, a line of dialogue cut from Curse of Fenric (One of the best later stories and well worth checking out, if nothing else for the moment where communism defeats vampires:)) has the villain become terrified of the Doctor, saying 'You're more than just a Time Lord aren't you?'
-With the black hole technology in place (And Omega apparently killed in its creation) the Time Lords were free to begin their exploration of time. To do this they created the TARDISes (Time and Relative Dimensions In Space), a semi-sentient type of dimensionally transcendant spacecraft able to hold vast spaces within an externally small shell. TARDIS development continues throughout Time Lord history and the Doctor's TARDIS (Which contains amongst other things, a library, a colossal wardrobe room, several bedrooms, an auxilliary control room and a large stretch of Wimbledon Common) despite being a Type 40 was considered an old and outdated model as far back as the series' debut.
-The Time Lords soon discovered the potential dangers of their technology, as it presented an almost irrestible lure to other races. To this end, TARDISes were fitted with Chameleon circuits, a camouflage system designed to blend the TARDIS in with it's surroundings. The Doctor's TARDIS, it should be noted, has been stuck as a Police Box for the entire run of the series. It has been clearly implied, on several occasions, that it likes the shape.
-The Time Lords are also unusually long-lived, each one capable of regenerating from fatal damage 12 times. In each case, the new personality retains all the memories of the old and seems driven to define themselves as quickly as possible against their successors. The regeneration can be triggered by simple old age (The first incarnation of the Doctor we see, who may not be the first incarnation of the Doctor but that's a whole different can of worms, dies of old age), fatal physical damage or can be self induced. Several of the novels implied that the Sixth Doctor, realising that he was ill prepared to face the threats that he sensed were coming, forcibly regenerated into the Seventh.
I think that about covers it. If you can track it down, I can't recommend A History by Lance Parkin highly enough. It's a huge book collating the complete fictional history of the series, from the early days of the Time Lords through to the end of time, incorporating every book, audio CD, TV episode and comic strip. It's currently out of print but the last edition covers up to the end of the first season of the new show at least.