Are there any other tower simulation games out there?
Honestly, there aren't many games like Sim Tower out there.
GameSpot lists these games  as being similar to Sim Tower
While searching GameSpot for 'Sim Tower' I found The Tower SP  for the GBA, which turns out to be Sim Tower ported to the GBA.
The best examples of newer Sim Tower games I could find are Startopia , which is supposedly a bit similar to Sim Tower, and a Sim Tower clone called Highrise Developer , an open-source project which is still in development.
I'm guessing the reason there aren't many games like Sim Tower is because Sim Tower was based on an elevator simulator . http://www.gamespot.com/pc/strategy/simtower/similar.html?om_act=convert&om_clk=gssimilargames&tag=similargames%3Bmore
Apart from the sequel called Yoot Tower  I only remember faint hints of a freeware\open source game similar. The links at the bottom of the wiki article mention a few resources for the game though the useful looking one is in Japanese. Google Translation might help with that.
It was years ago when I heard about an open source game, and I believe it died long ago. (Pitty, I am a huge fan of the game style as well.)
Hope that gives you a starting point.
Update: Here is a Google translated page for Project Tower . Hope this gets you on a good trail. http://en.wikipedia.org/wiki/Yoot_Tower
There's also a somewhat recent (within the past two years) Japanese release for the Nintendo DS, called The Tower DS. At the time of this answer it was available for purchase from several importers and shows as not being region-locked (thus, you can play it on a DS that's not Japanese).