You could always try make-up. If you stick to neutral colors you may be able to get away from the masculine without completely going over to feminine. You could even use contouring a bit to soften any sharp angles/features of your face. Sometimes a smoky eye in combination with a little stubble can be quite striking - you should see pictures of some of the work the late Kevyn Aucoin did on male models. Also grooming the eyebrows is not too difficult to do but can really make a big difference if you are trying to lessen the "masculinity" of your face.
I think that I would be interested in an appearance that would allow my clothing to indicate, though not necessarily determine, my gender expression in the eyes of other people. For example one day I might want to wear a classic suit and tie and be seen as a guy, and the next day wear a dress and heels and seem more like a woman.
You could try getting a more feminine style short haircut that you could style depending on how you want to present. Also you could try growing out your fingernails, just a touch - like millimeter or two- and then shape them a bit when you cut them. Two other things that could help give you a more ambiguous look are: shaving body hair and using lotion to soften your skin. (and this was already mentioned but a really light foundation & natural looking makeup when you want to present more feminine. You could even get something like lip stain, that just barely darkens your lip color. Its almost not visible, I've got one by cover girl, it looks exactly like a felt tip marker.) Hope this helps
Soooo....quick update. I have started using skin cleanser, exfoliating stuff, and moisturiser. My skin is softer and I am getting an cleaner shave. The next thing is that I might try a two edge razor to see if it results in a cleaner shave. I tried shaving my underarm hair recently but that was unsuccessful. The other thing I might try is nails... But I might need to keep them shorter on my left hand, being a guitar and mandolin player.