Super Mini Bluetooth USB 2.0 Adapter

GoldenGadgets.com offers this Mini Bluetooth USB 2.0 Adapter for $2.99. Add coupon code "ENDSUM09" to your cart to cut it to $2.69. With $1.22 for shipping, it's one of the least expensive Bluetooth dongles we've seen. (It was a buck less a week ago, since expired.)

Note that you can get free shipping from Hong Kong, although it's likely to take substantially longer.