Check with your broker, they might provide a free one (I know mine does), or your local board may have an iframe you could use. If you want to go as low-cost as possible, those are your two best choices (at least in my humble opinion).
When you are ready to spend some serious money, head over to REW or Diverse Solutions.
A middle of the road would be idxbroker, which is who I use until I can afford to go with the big-money idx.