The F8T100 is a Bluetooth USB Dongle from Belkin. The device itself is tiny (though not as small as some dongles) has an impressive 100m range. It comes with a 1.5m USB extension cable, so it can either be plugged directly into a free USB port, or it can plugged into the extension cable if you are tight on space. The box also contains a quick-setup guige, a slightly more comprehensive user manual and a CD containig Windows software.
The device is based on a Broadcom chip, and functions like most other Bluetooth interfaces (be they USB, PCMCIA or on-board). The increased range (most devices only support a 10m range) is partially due to the slightly larger electronics and a flip up aerial on the side of the device.
Creating a new connection is simple using the provided Wizard, and once created in this way, a connection can be restored quite easily.
Not all that much software is Bluetooth aware, so you will find that you need to setup a serial connection ending in a virtual COM port, which you can then use to connect application software. Nokia's PC Suite works in this way.
One problem I did find was that if the device is inserted whilst the XP Pro (but not XP Home) is running, the machine will hang. Similarly the machine also hangs when the device is removed, as there is no "Remove Harware" icon for this device.
I have successfully used the Nokia PC Suite with my mobile phone and created both Data and GPRS connections using it's built-in modem.
Once installed, the basic procedure is to plug in the dongle with the machine running. Hotplug will load the appropriate kernel module, then as root you must quickly identify the USB bus and device number and run bluefw to download the firmware into the device (it gets wiped every time the device is unplugged). You then need to start hcid, preferably using the supplied init script. You should then be ready to connect to other devices. A good place to start is the collection of links at the Bluetooth and Linux page.
If all this rather unglamourous command line based stuff doesn't get your juices flowing, then there are two graphical front-ends with which Bluetooth devices can be controlled. The most advanced is the KDE Bluetooth Framework, and this allows devices to be browsed and connected to graphically. Amongst the connection types are Obex and Voice gateway (allowing your PC to be used as a speaker phone!). There is also a GNOME Bluetooth project, but this is lagging behind the KDE one by some way.
There are also a number of client applications which may be of use. The excellent, but rather old, Gnokii provides a graphical interface to Nokia phones allowing access to their Address Books, Calendars and SMSs (including the ability to send SMSs). By contrast GAMMU supports a wider range of phones, but is non-graphical. It provides the ability to send and receive picture messages, backup your phone, and even install Java applications on your phone. These tools expose a far lower level of detail of the phone than the coresponding Windows apps.