Is there any way to do USB over Bluetooth (i.e. Connect to an external HDD via a bluetooth bridge of sorts)?

Maybe it is possible to build bridge with an FTDI chip (e.g. FT232) which is a USB RS232 converter and with Rayson BTM-222 module which is a RS232 BT converter. On the receiver side you should have an opposite order of mentioned devices.It is just an idea, I haven't assembled anything like this before ;).

Not directly. USB requires a host interface, so minimally you need some kind of USB host device with bluetooth on it which supports the device you want to control. An external drive requires the right kind of endpoint.

Also bluetooth isn't very fast (which profile were you thinking - serial? Audio? Obex?).

Whatever you may want to do - since you weren't specific as to goal - might be expensive and/or complex. Yes, I could do it, but you would need maybe an old PC or laptop... That said, it is easy to read and write SD/SDHC cards, and they go up to 32Mb, so work well in embedded via SPI. Whatever you want to do, it might be doable, and even easy.

For example, the EyeFi will upload any valid JPEG in the DCIM structure over WiFi. I've used this to copy logged data to my Picasa account (I also have qrcode to jpeg which fits nicely in an arduino, but you can use single black pixels with a lot of metadata fields).

The Bluethooth is too slow to USB profiles. The BT is 2.1 Mbps, USB 1.1 is 12 Mbps and USB 2.0 is 480 Mbps. That is the reason because the wireless USB specification don't care too much over Bluetooth as transport.

The Bluetooth 4.0 will be WiFi. The best way to do this is to use USB over IP (from FabulaTech) Server (WinCE or Linux ARM) on the HDD side and USB over IP Client on the desk side. You can use bluetooth to transport the IP packets, and then USB over IP but I don't recomend it.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.