A friend of mine from shul has designed a very clever solution to the problem of how to put your Chanukia in the window without rearranging all your furniture.
It's a simple shelf that clips onto a standard (Israeli) window ledge. It is sturdy, but doesn't require any screws or fasteners, and after Chanukah you can remove it and it doesn't leave any marks.
Best of all, he practically gives them away (25 shekel for the basic size which is big enough for a single chunkiah).
For further information, check out the following web page I threw together for him:
He's also looking for agents in other parts of the country, so if you would be interested in making a few shekels between now and Chanuka, feel free to call him directly, or if you prefer you can contact me (or leave a comment), and I'll put you in touch.