I have had a sharebuilder account now for about 2 1/2 years now. Easy to use, helps you get started buying shares at pace that you can afford. Be careful on how you are going to invest, even with your low weekly, monthly, or how frequently you decide to invest, this is a long term decision. It can be tempting to withdraw you money with the market swings.
Wish you the best of luck if you decide to open an account.