What is the best online stock trading platform for beginners?

I am just now looking to invest some money in some penny stocks and such. Nothing serious, just a couple hundred bucks or so….just to learn how it works and get started. Which platform should I use with regard to making LOW DOLLAR AMOUNT TRADES… Scottrade, etrade, ING, forex, etc….
When I say low dollar amount, I mean around $200.00 per transaction…that seems like a good dollar amount I can learn the ropes with.

I think this site, sogotrade is pretty decent, $3 per trade, and gets 100 free trades.

http://www.sogotrade.com/Default.aspx

good luck my fd.