Trading Stocks on the Mac? Any good apps?

[Mr. Mayor]

As an active investor, I rely heavily on an adviser or two that give me sound advice... However I've always wanted to fiddle around with the market myself. Just me vs. the world

Does anyone know of any software/apps out there that let you trade online? I know there are a lot of services out there (ameritrade, scotttrade, etc...) but I'm pretty sure the active trading apps are not built for OS X.