Are bluetooth dongles specific to particular devices or is any dongle compatible with anybluetooth device?

Bluetooth is an industry standard so all bluetooth devices should be able to connect to each other. So I would say that any Bluetooth dongle could connect to any Bluetooth device.

For the most part this is true, but some bluetooth devices are specific to the device it will connect to. For example, I have an iPaq RX3115 with built in Bluetooth and a had a set of bluetooh headphones. I also have a D-Link Bluetooh dongle for my laptop.

The headphoines would only work with the iPaq. However I was able to get my GPS receivers to work both with the iPaq and the laptop.