I'm not sure if these are the best, but I'm using Bloomberg and E*Trade Mobile Pro for iPad. I use these on my iPhone as well and the iPad versions take advantage of the bigger screen.
E*Trade has some nice features using the larger screen. Top has multiple little windows and bottom is about half the screen - you can swipe to flip through your stock list vs watch lists on the bottom. Selecting an individual stock/fund will update little screens on the top which give you the detailed quote and chart (1day, 5 day, 1 month, 3 month, etc.) The cool thing is that as you touch a stock on the bottom, the quote and charts update instantly, so its very quick to get the detailed quote and chart view with 1 finger press and you can switch very fast to get updates on all in your portfolio or watch list. No offline, no downloading. But you do have real time market news, alerts, and CNBC Video (if you are a pro subscriber). Trading, however, seems to be much better on the iPhone, especially when you are changing an existing order.
Bloomberg does quotes, charts, news without an account and was rewritten for iPad. It handles some International quotes, but I have not looked at foreign stocks very much.
Hope this helps a little. I'm sure others can share more about other apps. By-the-way, if the iPad app is not fully featured, you can still go back to the Web browser method and access like you were on a laptop.
