Can anyone recommend a good bluetooth adapter / dongle for an iMac late 2010?

Hm. I don't work for Apple or anyone at all, but I've had good luck with iogear stuff. Supports mac no problem. just look on the package. You don't need drivers, just plug in and go. You'd also have to go to your Bluetooth menu and make your Mac Discoverable. I think I can understand why you're asking this question, sorta. If your Bluetooth module has gone bad, eg if you go to About this Mac then system report, and it doesn't show up there, under hardware/bluetooth, then yes, a dongle absolutely. Getting in there and replacing it is a mighty tricky piece of work

john b