Well Card Player is a free site offering odds on hands for all the poker games. It is quite interesting for me as obviously I have come from a Horse Racing Gambling background. It all amounts to the same thing, you don't bet something at 2/1 if it should be 5/2 and you don't lay something at Evens if it should be 4/6
So in Poker you don't call a bet if you are getting 2/1 pot odds and you're a 3/1 shot to win!
As we all know there are punters in all forms of gambling some are shrewd some are mugs. Let's be honest, we are mainly traders on here but it is still gambling by definition but it is a more cerebral form.
I find most bad gamblers hold onto the belief that it's all luck. They do that as it means when they lose it can be put down to bad luck but when they win they claim "they knew it would win/happen"
I find in racing you will never convince a bad gambler he is wrong no matter how cogent your argument! I have tried to help friends who gamble to understand more about odds and how they work but to be honest it's like peeing into the wind. After a few attempts you just get fed-up and give in.
You've heard me mention on here the lemmings diving over the cliff edge. You know the ones, I said you buy one you get one free..trust me....oops!

Here is a screen shot of a poker game, I am playing Omaha. Pre flop I am around 67% to win the hand should it run its course. Post flop I am an underdog and dependant on the size of my opponents bet I may have to fold as I am 7/4 and the pot may ofifer less. My opponent checked which is strange when you consider he a favourite with the straight draw. I have a lot of cards (outs) to improve my hand and his check gives me a free card which comes the 2clubs. That means I am favourite now and about 2/5 to win. Surprisingly well actually it's unsurprising that at this stage he chooses to bet and bet large! I have to raise at this point and he went for it. He is now around a 9/4 shot but his odds both pot and implied are all wrong. The river was a club and I won the pot. He then starts moaning because I caught a lucky river card. Like I said about bad gamblers they don't look at the odds available and bet when they're in their favour.
I feel if you study odds and book percentages (including over-rounds) it will give a better insight into how markets form. You tend to get a "feel" for how high or low a price will go without the book going crazy.