Kato and GX hopeful. I use Ameritrade, or APEX to some of the old timers. I am very satisfied with their service, $10.99 for a buy of any size, and $10.99 plus a very small SEC charge (seldom over a nickel) for sales. I've found the site easy to use and transfers to/from my checking account take about 1 1/2 to 2 days.
The problem of the wait for $ to be available following a sale only comes about if you have sold stock you recently purchased, lets say within the past 3 days. They say they must wait until they have the purchased stock confirmed, or basically in their hands, before they will post the cash as available in your account if you sell it quickly. It will show as an account balance, but won't be in the available cash area until the "buy" is confirmed. So, if you bought something 3 or more days ago, no problem. If you bought something 2 days ago and sell today, the $ may be available in only one more day. But, if you bought yesterday or today and immediately sold it, you may have to wait up to 3 days to have the $ available for you to make another buy.