For me, my most recent discovery was that there are new conversations at the Underworld Bar if you go there after the UNATCO ambush of Paul's apartment, during Mission 4. This wasn't exactly "recent" (I found it out two or so years ago) but I've had a copy of Deus Ex almost since it was released.

Last playthrough just for poop and giggles I used the ghost cheat in Hong Kong...

Instead of leaving the Lucky Money Club and going back to the market I did the cheat and discovered an MJ12 trooper on an upper staircase (one of the two that's by the main VersaLife entrance in the Market area).

The soldier showed up green im my IFF. He didn't talk or move, but was a nice source for a few items after I amputated his head. }:-)