A few days ago, I found a feather hitchhiking on my pants leg so I thought it would be a good choice for my next spiritual symbols article.  
    A feather is a light, airy thing so it usually represents lightness, rising, the heavens or ascending to spiritual worlds or dimensions.  They can also represent truth and honesty, especially spiritual truth.  The wearing of a feathered headdress, robe or cape represents power and knowledge, especially the power and knowledge of birds meaning the ability to fly above earthly things and ascend to higher realms.  Two feathers together represents the two great forces: Yin and yang, hot and cold, male and female.
A white feather can represent clouds, but can also represent cowardice.  A black feather usually represents something ominous.  A crown of feathers represents the rays of the sun and deities that wear feathers, or have feathers, such as  Quetzalcoatl represent the spiritual sun.  In some Native American tribes, Eagle feathers represent the Great Spirit or Universal Spirit.  When priests and shaman wear feathered cloaks, it represents the ability to travel to other (spiritual) worlds.  Since angels are often depicted with feathered wings (I've explained before that this is a symbolic, not literal representation), feathers can also represent communicating with or emulating angels.