I would like to know whether it is possible to establish a bluetooth connection to my duemilanove using a FTDI FT232RL board like this one
and a cheap bluetooth dongle that plugs into the board's USB connector.
thanks in advance,
No, unfortunately not.
The FT232RL is not capable to act as an USB-host, while the dongle needs one.
If it was possible you also wouldn't need an FT232RL-board since the duemilanove already has a FT232RL chip on board.
Building (and programming) a USB-host application for an arduino may be possible, but is quite hard to do and probably not worth the trouble.
A simpler way to do this is probably using a Bluetooth module that's TTL-RS232-based.
Sparkfun has a reasonably priced one, http://www.sparkfun.com/products/9913
Ebay shows similar, cheaper, boards when you enter "Bluetooth RS232" (and/or TTL).
There is also a ready to use bt-shield for arduino.
They all.... seem to have a similar CSR-based chip (which you may also find in a dongle),
but I'm still not sure what I should buy, I guess I'm still doing a similar search as you. ;)