By now, it's probably fairly common knowledge that you can use your WesCard at the vending machines in Usdan (no points, though--just Middletown Cash that you've put on). Until now, those were the only ones. Not anymore. Three of the four vending machines in the basement of Freeman (all but the Powerade one) have been outfitted with WesCard readers:
They aren't working yet (they all say "NOT IN SERVICE 001" or something to that extent), but I imagine they will be soon. Hopefully this means that every vending machine will soon have this capability. I haven't noticed any other machines that now take WesCards; if anyone else knows of any, post them in the comments.
Be prepared for disappointment if you want to put some Coke on your WesCard. David Markowitz '11 points out that the vending machines (all except the ice cream machine) near SciLi now have card readers... but that none of the card readers work. Oops.