Opponent is pretty new to the table but hasn't shown anything impressive yet. He is somewhat loose and bets weak amounts.

PokerStars No-Limit Hold'em, $0.50 BB (9 handed)

SB ($36.55)
BB ($15)
UTG ($58.90)
UTG+1 ($169)
MP1 ($37.20)
MP2 ($38.25)
Hero ($55.20)
CO ($34.75)
Button ($16.85)

Preflop: Hero is MP3 with , .
UTG calls $0.50, 2 folds, MP2 calls $0.50, Hero calls $0.50, CO raises to $2, 3 folds, UTG calls $1.50, MP2 calls $1.50, Hero calls $1.50.

Flop: ($8.75) , , (4 players)
UTG checks, MP2 checks, Hero bets $4, CO calls $4, UTG folds, MP2 folds.

Turn: ($16.75) (2 players)
Hero checks, CO bets $2, Hero calls $2.

River: ($20.75) (2 players)
Hero checks, CO bets $2, Hero calls $2.

Final Pot: $24.75

Results in white below:
Hero has 9s Js (one pair, nines).
CO has Jh Qh (high card, ace).
Outcome: Hero wins $24.75.

I decided to bet out to see what he thought. He thought and thought and called it. I was ready to fold the turn but he bet so weak that I called. The river was the next worst card but for those odds, I called which I will admit was kinda of a curiousity call. I didn't expect to have any chance of winning. Is my half pot bet on the flop what caused all this? I figured if he called, he had overs and like AK or AQ or maybe AJ but as long as that didn't hit on the turn, I felt I could take the pot. Comments?

Preflop
Fold it instead of calling, then fold it again when it gets raised behind you.

Really though, J9s does seem a bit marginal, but I guess it's playable 2 from the button at a loose/passive table. At least you have the raiser behind you so you can CR the field if you hit a monster and know the odds if you get a draw but... I think it's a very marginal preflop play. I guess from your sig that you tend to play this particular hand no matter what though

Flop
Top Pair mediocre kicker, with a flush (and unlikely straight-) draw... yeah, betting out seems to be the best choice but if you're protecting your hand against the draw you should obviously bet more... so I guess this is more of a probe bet (Harrington style! Something I thought was scorned here!). His call seems very... odd. I'd expect a raise or a fold here. If he has an overpair he should be raising, I'd probably put him on a flushdraw with something from AKs to KQs... or he could be a muppet with just OC's.

Turn
Urk. Scary card. Odd though, I'd expect him to have the if he was drawing... his bet is just über-weak... I hate these freaking losers/muppets/smacktards that weak-bet, so I'd probably call or raise it as well.

River
This really is a pet peeve of mine. The super-weak riverbet. Really, what's the f-ing point! I call this out of spite (I've stopped raising them because they invariably call with something marginally better... like Q9 in this situation.) and to get information on how he plays, I on't expect to win (on the other hand you just need to win 10% of the time to make a nice profit so it's probably correct).

Result
Freaking muppet. I love players like this though, they are by far the ones you make most money from.