I don't know about the best but I bought one of the cheap eBay ones for £5 and it works fine. Charges and sync's my iPhone too. Only problem is that it is white and I would have preferred black and the blue power LED is a bit bright but what do you expect for the money. It holds the iPad at the perfect angle and is stable that's all I really want from it.
We like it. It'll play your music and charge your iDevice as well. Also has a rechargable battery for portability. The sound is ok, but if you're looking for something with high end stereo quality this probably isn't for you. And despite what some of the reviews at Amazon say, it can be used with the iPad 2.