There are a lot of iPad accessories which are specifically designed for the iPad 2.  However, it can be really pricey to upgrade all of your accessories when you purchase your new tablet.  If you already have an iPhone, you will likely be able to use your existing accessories on your iPad.  However, they might not work as well and will require some adaptation.  The docking speaker iPad accessories are one example. 

There are quite a few speaker docks which have 30 pin docking connectors which will work with the iPad, even though they were actually made for iPhone and iPods.  Since there are only a few companies which have bothered to make docking speakers specifically for the iPad, you might even have to resort to the iPhone version.

The main issue with the docking speaker iPad accessories is that they require a lot of power.  For iPhone and iPod, the docking speakers are great because they will actually charge your device while you play music.  However, the iPad requires A LOT more juice to run than its predecessors.  You are probably going to lose juice on your iPad battery while you are playing music through the docking speakers.  Note though that you may be able to get a bit of a positive charge on your iPad battery if you turn off the iPad screen while you are playing music.

Instead of investing in a whole new docking speaker system for your iPad, you might want to consider a dock extender cable instead.  These iPad accessories are made so you can hook up your iPad (or many other devices) to the desktop speakers.  Then, you can use your previous iPhone docking speakers easily for your iPad.