it doesnt really even matter if they are real or made up prices. thanks, BD p.s. I already tried a google search!
How long do you want to simulate? Most brokers have a 2 weeks trial period, so just sign up with them. Also, what do you want to trade? If futures, here is the T4 platform: http://www.ctsfutures.com/t4.aspx P.S.: There is no completely free trading sim, but there is extended trial periods....
ThinkorSwim offers a free papermoney account - https://www.thinkorswim.com/tos/displayPage.tos?webpage=paperMoney
One of the best free ones with real market data is NinjaTrader. It has tons of brokers support that allow you to connect for free.
NinjaTrader has a built in simulator that will make up prices, but it also have Market Replay where you play back real data from prior days. Both of these options are completely free. You can also go with something like MultiCharts where like NinjaTrader you can plugin to a bunch of different demos if you only need it for a short period.
To get live streaming data with Ninja Trader you need to pay for the data so its not free. You can only get delayed data for free. Same thing with ThinkorSwim, I believe it's delayed 15 minutes.
If futures, demo ninjatrader is free. (free CQG data from AMP futures or Mirus) If stocks, it's harder. I used to DEMO a cool instaquote platform through directaccesselite, but they seem to have gone bust (the broker) There must still be some around who will let you Demo their equities software in realtime without restrictions.