Nice. I do the same thing but my returns aren't that high, maybe between 20% and 30%. I use Google Finance as well.

My strategy is simple: I look at the day's biggest losers and, if my research says it's an overreaction/emotional, I'll buy in the hopes of selling in the next week. Most of the trading comes around earnings time. I had a pretty good return with Groupon (I sold too early though), Verisign, MMR and a few others.

I found I was spending too much time checking the screen when I should have been working though, so I just bought about 100 shares of Apple when they dipped below $520/share recently and hope to sell early next year when they get back up to $625 or so, hopefully after Q1 earnings.

By the way, this isn't a passive strategy for me. I use stop and limit orders, but it takes a lot of time to keep track (at least for me, but I'm not very efficient), which gets especially difficult when I'm traveling and the market stateside doesn't open until 7pm (bleh).