I work in the prep room of the crown and bridge department at my lab. I pour models, grind models, read rx, paper work for incoming cases, I've learned about a lot of different materials, I trim preps, mark margins, I pour dies, I make duplicates for white wax ups, I set bites, articulate bites, and probably more that I just can't think of right now. I do all of this for cases involving implants and partials as well.
I literally feel like I learn something new every week and I've worked there for almost two years. No case is the same and you have to learn to recognize when an order from a Dr. might not work. Since I'm pre-dental my boss has made a point to teach me as much as he can. I've gotten chances to observe other departments when we're slow. There's a department that scans in the trimmed preps to mark the margins in a computer and the porcelain people.
It's seriously the best job ever. If you can find a job at a dental lab I would recommend taking that over a job assisting a Dr. I've assisted before and working in the lab teaches you sooo much more. I know that I won't actually be doing this much lab work in school or my office someday but the background knowledge I believe will only make me a better dentist.