With this app you can manage all of your investments and transfer money between accounts, get real time market quotes, and easily trade stocks, mutual funds, and ETF's.
This is just the initial version of the app, though, and it appears that a lot more is on the way in the future, including mobile deposit, streaming quotes, and branch locator.
Update 6/7/11: Remote deposits by simply taking pictures of your checks are now live - that was fast (thanks, @dcplaya)!
The app is available for free in the Android Market.
Schwab Mobile