Edit 24/06: Bluecore4-ROM dongles may work too!
It is quite difficult to tell if a usb dongle will work or not (even for CSR chips).
And not to make it easier, dongle manufacturers can change the chip without changing the product name… So be careful about hardware revisions!
I suggest CSR chips such as BlueCore2-ext and BlueCore4-ext. There is no guaranty it will work.
Older CSR chips may work (as the dongle I’m using – Cellink BTA-3000).
A list of dongles with BlueCore2-ext can be found there (p.98-104).