Yeah I feel your pain there, I have the iPod touch 4th gen and I am not sure if any docks even support that fully, the last time I checked there was none. I think its an issue with apple's restrictions on charging, they can only charge with the Apple USB cable and charger from the apple store, there are third party chargers that work too, but those are few and far between and most give "charging not supported" errors. A lot of docks also charge your iPod while you are listening. Most docks just say supports 3rd gen iPod touch and later, or they don't say at all which iPods or iPhones they support.
The best thing to do is to buy a dock that has a standard headphone jack and plug the iPod or iPhone in through that, that is what I do. I have a little iHome dock that I paid like $20 for and its lasted me forever. The cord is short so I have an extension cable because the headphone jack is on the bottom of the iPod and that is where its supposed to sit on the dock, but it obviously doesn't sit on the dock since the jack is in the way. You can always be sure it will be compatible with the headphone jack no matter what (plus you can plug other devices into the dock if its just using a headphone jack), if you just want to play music out of it and if you don't want fancy features like charging while on the dock then this will work for you.
