If you're searching for an affordable service to trade stocks online, you should take a look at Questrade.com. Questrade is a Toronto based direct-access broker that offers a per trade price from $4.95 to a maximum of $9.95. They also have no activity minimums, no inactivity fees, and 24-hour account management.
Use offer code redflagdeals when signing up a new account with a minimum of $1000 and you will also receive a $50 rebate. Additionally, if you move an account with a minimum of $25,000 from another Canadian brokerage, Questrade will pay your transfer fees up to a maximum of $150.
If you're looking to do more research, there's a long-running thread in our personal finance forums that discusses Questrade with over 2000 replies.