The Bird Banding Lab recently sent out a note to banders describing a new website that looks like it might be useful to banders when it comes to having photos of birds in the hand that will help age and sex different species. The site is called Piranga and it is found through NatureInstruct. Not only is it a source to use, it is also a site to which banders can contribute.
When trying to determine age and sex of birds it is often necessary to look at every feather of the wing and/or tail along with other characteristics depending on the species.
Registration is free and as a disclaimer I am not associated with the site at all (but wish I was).