TwonkyBeam now works with the Denon AVR-3808CI. Setup is easy. Just connect an Ethernet cable to the reciever and set the "Source Select" knob to "Net/USB Stereo". Now you should be able to beam MP3s to the receiver. The only known issue is that you can't control the volume remotely using Beam.
If you're a PC user and don't have Beam already, you can download it for FREE here: http://www.twonkymedia.com/downloads/TwonkyBeam_Setup.exe