NIN are definitely at the pop end of industrial. I used to really like the first album and the Quake soundtrack is actually a pretty decent bit of ambient-industrial, if you dig that sort of thing.
So yeah, if you like danceable pop tunes then investigate the early stuff, which owes a good deal to Gary Numan, Depeche Mode and so on. I don't know his later stuff well but it went very concept-album-y (so, er, not so pop then, I guess) and self-consciously serious, albeit in an adolescent sort of way.
I stopped bothering with them after I got more into the Ministry/Revolting Cocks and Front 242 side of things. (Having mentioned Ministry, I now predict that mistersloane is going to pop up and say "Don't listen to Ministry, they're boring, listen to Foetus instead".)
SMB is right of course, TG and CV basically invented the genre and between them produced a body of work that varies from unsettling ambient weirdness to harsh walls of noise to slick dancefloor disco tunes. Another early group worth checking out is Einsturzende Neubauten, although they're sonically very different - think metal-on-metal percussion, found sounds and screeching punk guitars rather than synths and drum machines. There's also bunch of great stuff from the late 80s/early 90s from Mark Stewart/Gary Clail/Tackhead, all of which was produced by Adrian Sherwood, and which sits somewhere in between industrial proper, hard rock, funk, dub and hip-hop.
Edit: should add I've recently started listening to Skinny Puppy too, another stalwart of the '80s EBM-industrial scene. Unfortunately many of the tracks suffer from the perennial Curse Of Industrial, to whit: great music, shame about the vocals.