Since my IRA accounts were with Vanguard and that's where, aside from emergency funds, my assets are, I used Vanguard for stock trades last year. At $7, their trade fees are pretty decent, but they don't have many tools to speak of.
Now that I have enough funds to begin trading outside my tax deferred accounts, I've been looking around for a new brokerage. My eye was on Scottrade, but TradeKing is running a decent promotion this month, so I decided to go with them.
http://www.thedividendguyblog.com/open-a-trading-account-and-put-50-in-your-pocket-promotion/