Which window manager / desktop manager are you using?
e.g. with Afterstep, you can middle-click on the background to get a list of window menu options, one of which is “move window”. After clicking it, you can then drag any part of the window to move it. Or you can drag it on the pager.
I don't know if Gnome and KDE have anything similar off hand but I'd imagine that they would somewhere.
On KDE, I think you can right-click on the backdrop (or possibly the toolbar, or a window's menu bar) and choose “cascade windows”.