There is a new product on the market which apparently all of the major photo manufacturers use for cleaning their lenses, etc. It is called Opticlean - http://www.caliope.co.uk/index.html
It is a polymer that you paint onto the lens, allow to dry and then peel off - it then leaves the lens completely clean wth no risk of scratches, etc. like you may get using a lens cloth. It is £9 per bottle (aprox. 25 uses). A lot of people on the net have recommended this for telescopes and it is also safe to use on mirrors.
I seem to recall peeps using this to clean CCD windows too. Not sure I like the idea of sticking anything to a lens, but unless it's got some very fragile coatings, I can see it working. Does it work on fingerprints and so on?h
I asked the manufacturers are here is their reply :-
"A cautious yes is the answer.
Opticlean is used very successfully for both these applications.
HOWEVER it is important that you become familiar with the technique for applying and removing the polymer before you try it on the CCD cover glass.
this is because you must be careful to apply it to within a mm of the edge of the cover plate but not over the edge. It can be difficult to remove if you allow it to flow over the edge or onto the mount of any optic.
With that caution, that you have worked with it on simple lenses to get the feel for how it flows and how to remove the cured film I can recommend it for both these applications.
Several amateur astronomical groups are enthusiastic users and i could put you in touch with some of them if you needed any further 'comforting'."