Can you use a USB hub to acess more devices?

I have a question, can you use a USB Hub to add more devices, Only reason I ask is that with the WD Media player there are only 2 USB ports, one I have connected to an external drive and the other for a wifi adapter. Would love to add a wireless keyboard and mouse for Youtube and facebook or whatever. Can this be done? 

Yes, supposedly you can use hubs for the KB and WiFi, but only ONE HD is allowed per main USB port. So, KB+HD on one hub should work, and perhaps WiFi, too.