Scottrade would be a bad idea. The good thing about having Scottrade as your first broker is that you are going to like most other brokers when you switch out of Scottrade. Etrade is a less bad idea. However, if you open an account E-trade, you actually still have to pay at least $9.99/per trade. If you do end up trading 100 times with the first 30 days, you'll pay about $1000 in commission before your first month is over. For a new account, E-trade will reimburse your first 30 days' commissions (up to 100 trades) about 2 months later. Moreover, if you don't stay with them for at least 6 months, they will charge those commissions back to you. Besides, E-trade has an account transfer out fee to make the parting even bitter.
Considering that you at least worked on trading concepts for a year or so, you might want to go with RML trading. I think they currently have $2.95 per trade for both direct and non-direct orders for a specific deal with new accounts. You can also choose per share pricing if you like.