A co-worker recently sent me an article by Emily Perl Kinglsey entitled Welcome to Holland. It was written with the experience of raising a child with a disability in mind, but I found the analogy she used applicable to our current situation - not being able to have a child - as well.
You can find a copy of the article here. It is quite short, and markedly poignant, no matter which way you happen to exist outside of the norm.