Now I'm giving a try to gvfs-mount. Currently I can mount a volume and list it with gvfs-mount --list, but I cannot browse inside it because it isn't mounted. I played with the --mountable argument, but it must be a joke. I think I need a something fuse daemon from gvfs... I'll keep this up to date.
Update: Everything is alright now. The output of
ps ax | grep gvfs shows the following process:
/usr/lib/gvfs/gvfs-fuse-daemon. All your mount operations will be available at $HOME/.gvfs.
The recent GTK+2.14 release introduces a widget to ask a password thats called GtkMountOperation (have a look at the GTK+ blog). It might be interesting to start a Thunar plugin, and release it officially with Xfce 4.8.
Update 2: And on a fresh Debian install (or in general anyway) don't forget to install the fuse-utils package (