Mounting Apple's products in Linux is not as straightforward as it should be. I have an iPod Touch 3G. It has iOS 4.3. The problem is that the libimobiledevice1 package in the Squeeze repos are too old and cannot handle that version of iOS. Forunately, the latest stable release of libimobiledevice can do that (I have not tested with iOS 5.0). In order to compile and install it you need the build dependencies of libimobiledevice1 first:
# apt-get build-dep libimobiledevice1
Then download the source of the stable release of it:
$ wget http://www.libimobiledevice.org/downloads/libimobiledevice-1.0.6.tar.bz2
Extract it to somewhere (e.g. /usr/local/src). Move to that directory, then configure, compile and install the library as
$ ./configure --prefix=/usr
# make install
That's it. You can use ifuse and gtkpod in order to upload music and whatever you want onto your iPhone/iPod Touch.
If you use Gnome DE, libimobiledevice1 is installed by default, and it is a necessary dependency of the DE. Note, that you do not have to remove it in order to install the compiled library.