Grief is the instictive human response to loss. It's a complex emotion and is natural and necessary. It is not "bad" and does not "make you weak" to grieve. It is not an illness or mental-health problem.
If you are grieving, it is normal and exactly what you need to heal!
Here are some resources to help you with grief.
Grief, Death, and Loss
Center for Loss and Life Transition: A private organization dedicated to furthering our understanding of and compassion for the complex set of emotions we call grief. Dedicated to helping both the bereaved, by walking with them in their unique life journeys, and bereavement caregivers, by serving as their educational liaison and professional forum.
Crisis, Grief, and Healing: A place where men and women can discuss, chat, or browse to understand the many different paths to heal strong emotions. Resources on the site include excerpts from author Tom Golden's books on healing from loss.
GriefNet: GriefNet is an Internet community of persons dealing with grief, death, and major loss. They have many email support groups. Their integrated approach to online grief support provides help to people working through loss and grief issues of all kinds.
Grief and Loss: Grief support information and resources from the American Association of Retired Persons (AARP).