I'm going to try this "guess the hole cards" thing, but only because I don't really want to hear the typical responses that you get to this kind of question.

On a Full Tilt $100 max (.5/1) table Player A makes it $4 to go from UTG. Folds to Player B 3 seats away in MP who calls. Everyone else folds.

Pot: $9.50
Flop: J[h]7[d]5[c]

Player A checks, player B bets $6, Player A calls.

Pot: 21.50
Turn: 8[c]

Player A checks, Player B bets $15, Player A raises making it $30 to go. Player B moves all in, Player A calls.

If you were observing this hand and didn't really have a read on either player other than that you hadn't seen them do anything crazy or make a horrible play what would you put them on?

Ummm....Player A - Aces or Jacks
Player B - a set.

A has to have JJ. If he has QQ-AA he played this horribly and since he apparently doesn't make horrible plays he most likely doesn't have QQ-AA.

B has 77 or 55. The 8 obviously didn't help him and he is confident that he can beat AA so a set is the only thing that makes sense.

KennyG hit the nail on the head. Now 2 people have read that Player A likely holds J-J. With a read like that, should I, Player B, have laid down my 7-7 when he check-raised the minimum on the turn?

Player A is running textbook ABC set play here, check-calling the flop and check-raising the min on the turn. When I was in the hand I thought to myself that his play was dangerously close to how many like to play sets and that if he had one the only one he could have when raising UTG was one that beat me, but between UPF and BTP everyone (or it seems like everyone in my mind) thinks that you should never ever ever lay down a set because set over set happens and you just can't do anything about it. I don't know that that is true in this situation, but I wanted to see if you all got the feeling that he had J-J as well without everyone just barfing "set over set = unavoidable" at me.

I'd have to be pretty confident to lay down a set if I suspected a higher one. Online, I don't think I could do it. This looks like JJ, but could also be a badly played AA or [Kc].

I would be worried...but I would still call. I said AA or JJ....I see AA played the same way at a lot of different places....

I'm one of those set over set "means you're always screwed" people.