Depends exactly what you mean by glare.
Assuming a standard understanding, your options are basically to block the light coming through the window, change the angle you take the picture from or to somehow 'hood' the lens. The last option will only work in certain circumstance.
If you just mean that your subject is coming out as a shadow because of the brilliance of the light behind it, you could use a fill-in flash - fancy name that, in the case of cameraphone, simply means, turn the flash to always on and hope it's bright enough to light the side of your subject facing the lens.
If you were using a proper camera you would have more options like using a polarising filter, balancing the flash or taking the light reading from the subject and letting the background burn out (i.e. show up as completely white in the picture) - these are not going to be an option on a phone where you generally can't easily use filters, control where the light reading is taken or control aperture, exposure and flash.
I guess you might be able to do something with photoshop or something similar ..
