Here's the product page for Thinkorswim, lots of good info on there from customers:
http://www.investimonials.com/brokers/reviews-thinkorswim.aspx
I'm on the $8.95 per trade no matter how many shares I trade plan...no idea what the name of it is, just pull up the handy Thinkorswim chat window and have a customer rep set it. Here's what I do to focus on shorting penny stocks:
http://www.investimonials.com/forums/recommended-brokers-for-shorting-penny-stocks-yes-its-legal--a-good-niche-strategy.aspx
I'm an affiliate too so of course I'm gonna say I love it, but i'm an affiliate of a lot of products that I don't love as much as this one...I hate most brokers, TOS is built to love...it's a little more expensive, but once people stop trying to save $5/trade and focus on earning bigger profits thanks to better borrows on shorts, better executions and amazing customer service, this is an obvious choice.
PS I don't use TOS software as I have always had success with Etrade PRO even though I don't use ETrade as a broker