There is a site called that "used" to only allow you to buy or sell shares in a stock only once a week, for $4 a trade. I see that it now has grown from that to allowing daily real-time trading.

It was something I would never be interested in because if you happen to snag a real loser, (or a good company that just ran out of favor, due to government policy change, etc), you'd likely loose all of your investment before you could get out of it.