Well there are scores of scams, main ones to be aware of:
1) Mis-quoting selling items on contract, like in the question, this usually happens with faction items, like ships or MWD's and BPC's listed as BPO's. Be cautious read through the description carefully for BP's right click and show info, if it has number of runs field its a BPC not an Original.
2.) the Isk game, one of the most obvious scam is this one. someone giving away free isk, or if you send them 100,000 they will send you 100,000,000. This is BS, and if it isn't a Hoaks it is likely someone who has hacked an account selling off the assets of someone else as payback or being mallicious, you don't get a free lunch (unless it's a corp mate or someone you know being generous and footing the tab).
3.) Courier contract scams.
a) the collateral scam, someone puts up a contract with a high collateral, and when you accept it's a piece of pyrite. 3 guesses what happens next, they keep your money.
b) sometimes connected to a, the end station is in 0.0, and when you arrive you can not dock, and so cannot forfil the contract, they keep your collateral, and in all likely hood blow up your ship.
c) It's a huge cargo (700,000m3 +) you have to go through low sec to get to destination, pirates are waiting for your shiney freighter.
d) Any combination of the above.
4.) Major Lowball - This isn't really a scam, more sellers or buyers error, totally legitimate, however I bet it leaves leave you feeling cheated. something worth 250,000,000 is on buy order for 250,000 or you are looking to buy something for 250,000 and pay 250,000,000 instead. Bottom line its easy to do and most common, and can easily be avoided (as all of these can) by common sense and taking the time to read the price/description carefully, also if you are the one putting up a contract you could be loosing a lot of money as someone gets a bargain, someone I know got a moros for 1.2M rather than 1.2Billion because the contractor couldn't type the right number of zero's.
These are the most prolific ones I have come across, if someone else has others be good to hear them, there are some I'm fairly sure are scams, but can't be 100% so won't post them up.