Dragbox -- had a look.

Dragbox is described here but the most up-to-date version can be downloaded here as a .tar.gz file.
I tried it today in Ubuntu Hardy on my Dell.
To install you must untar (tar -zxvf file.tar.gz), CD to the new directory and configure (./configure). For me the configure completed without a problem. Then its just compile (make) and install (sudo make install).
Dragbox has a reasonable manpages which I reproduce here:

EXAMPLES
dragbox . file1.txt
Adds the current directory and file1.txt to the currently
running dragbox, or creates a new one. If file1.txt does not
exist, its name is added as text.

dragbox -t "Dragbox is cool"
Adds a text snippet to the currently running dragbox, or cre‐
ates a new one.

dragbox --get -0 | xargs -0 tar cfz backup.tar.gz
Get current items and pipe to xargs to create a tarball. Note
that this simple command will have problems if contents
include text items.

dragbox --name remember .
Put the current directory on a shelf called "remember"

TIPS AND TRICKS
Dragging in gnome works very well, but there are some hidden tricks
that can make some things easier.

Pressing modifier keys can switch between different types of drags;
dragging a file to nautilus normally copies it, but you can hold
shift to move it, or shift-ctrl to make a symlink.
You can drag from any window without activating it by holding the
altgr or super key when you drag. This is often very useful.

You can bring up a minimized or obscured window while dragging by
hovering momentarily over it’s button in the window list (in the
gnome-panel)

Just like minimized windows, you can switch workspaces while drag‐
ging if you hover over the workspaces switcher for a short while.

If you selected something in a window and focus another window, it
looks like the selection disappeared. In many cases it’s still
there, you can try to drag it without focusing the window (see
above)

Type escape while dragging to cancel the drag

ACCESSING DRAGBOX
Dragbox needs an X session to run and display its shelves. However,
to access dragbox shelves from non-graphical sessions, all you need
is to make sure dragbox knows which X session to connect to. It
might be enough to define the DISPLAY variable.

Dragbox seems to work fine, although it gives errors in the terminal (I launched it from a terminal) about some dbus error which don't seem to affect it at all.
So, for example I can use the command

dragbox file.txt

to bring a text file to the dragbox without physically dragging anything.
OK, so it works but I have to admit that, right now, I just can't see that this is going to be of immense use to me. Indeed, I just can't think of any circumstance where I would use this at all.
Maybe I'm just too ignorant to spot the benefits but I'm very willing to learn.

Edit (21-09-2008): Just installed it by same method in Foresight 2.0.4 on the Dell. Works just the same. Now if only I could find a use for this tool.

Edit (21-09-2008): This is a useful review which goes someway to explaining the benefits of Dragbox. Indeed, one immediate benefit is that it brings a multi-item clipboard to Linux (much like Shadow in OS X).