Monoprice has the Monoprice Bluetooth Music Receiver for $15 + $3 shipping = $18 shipped. Features supports 3.5mm aux output audio, A2DP audio streaming, and USB port for charging devices.
I just bought one of these a few weeks ago. I did have a problem with noise on one of my amps but the others worked well. I finally solved it by powering it through the included USB port. This is the first device I have ever seen that takes power through a full sized USB port instead of using a Micro or Mini USB. It also does not come with the USB power cable. The other issue with these is you can't change the device name so owning several of them is a challenge since it's not easy to tell which you are connecting to. You also can't change the device PIN so anyone is able to connect. Your next door neighbor may decide to blast Motley Crue at 4AM. Despite the drawbacks, the sound quality is acceptable but probably not up to audiophile standards. The range is also acceptable and it generally will not lose signal if the BT transmitter is in the same room. So far, I have used it with a DroidX, Iphone4 and Ipad2 with success. I also have the Belkin unit recently seen here and it seems to be about as good as this one minus the noise issues.
I just bought one of these a few weeks ago. I did have a problem with noise on one of my amps but the others worked well. I finally solved it by powering it through the included USB port. This is the first device I have ever seen that takes power through a full sized USB port instead of using a Micro or Mini USB. It also does not come with the USB power cable. The other issue with these is you can't change the device name so owning several of them is a challenge since it's not easy to tell which you are connecting to. You also can't change the device PIN so anyone is able to connect. Your next door neighbor may decide to blast Motley Crue at 4AM. Despite the drawbacks, the sound quality is acceptable but probably not up to audiophile standards. The range is also acceptable and it generally will not lose signal if the BT transmitter is in the same room. So far, I have used it with a DroidX, Iphone4 and Ipad2 with success. I also have the Belkin unit recently seen here and it seems to be about as good as this one minus the noise issues.