Robinhood is pretty cool. No fees to create an account and you get a free share of a stock when signing up which is neat. When creating an account you can put in even $5 to open.
Lots of good reviews of Robinhood out there. Full disclosure: If you click my link you and I each get a share of a stock. With the market down it might be a good time to buy in to the dip and benefit when the correction passes.