I have a download of a world called Maxis Island that is all of Sims 1, with a lot of extras, but its not 100% faithful and comes unpopulated. The terrain is all there though; it has ALL of Sims 1's expansion pack areas in one world, and several new regions that can be worked on. It supports every expansion pack from Sims 3 out of the box, and the only career thats unaccounted for are the Music career in a rather odd 'oops', and the ITF careers.
I'd recommend this world for builders, as the world template is so good; it just needs more accurate lots built and the various Sims 1 sims made to populate it.
I have that as one of my longterm goals (ive already made the Goth and Bachelor family, all the ghosts in the Goth graveyard, and ive even made the Pizza delivery guy) but its on the backburner while I slowly remake Sims 2 content. I plan to remake the always-forgotten DLC families for Sims 1 too, like the Maximus family with the ridiculous house.
I found Maxis Island here on the forums.