For glueing feathers I use a product called "Fish Glue". In Canada it is sold by Lee Valley Tools http://www.leevalley.com/en/shopping/Instructions.aspx?p=41041 They offer it for using with wood for furniture-making.
I find it dries quickly, remains clear, and holds well. However, it is not water-resistant, nor particularly flexible when dry. It does resemble the glue that was traditionally used on feather pads though.
E6000 works well. It dries clear, is waterproof, and stretches to a certain extent. The glue is pretty viscous so you can control the amount that goes on the feather without it seeping through very much.