Bereavement due to suicide is uniquely difficult; deaths by suicide leave survivors struggling with thoughts that this should have been preventable, that their friend or loved one chose to end their life, and all too often with shame and social stigma instead of the community support that would be forthcoming if the cause of death were anything else.
Here are some links with information and resources:
List of normal reactions to suicide loss. From the Canadian Association for Suicide Prevention. A comprehensive list with some entries that may surprise - in a comforting way. This site also offers coping strategies, memorial information, and resources.
The American Foundation for Suicide Prevention's "I've Lost Someone" web resources
"Beyond Surviving" at survivorsofsuicide.com - other resources here also. Note that although there is much helpful information available to the general public, membership at this site requires paid registration, albeit at a reasonable rate.
Survivors of Bereavement by Suicide - excellent UK-based resources
Common Experiences with Suicide Bereavement Great info from the SCBS in Australia.
Healing from a Spiteful Suicide Note and the general suicide bereavement survivors section at speakingofsuicide.com
The American Association of Suicidology's bereavement toolkit and resource list
Alliance of Hope for Suicide Survivors A community-oriented resource.
Excellent in-depth article specifically on supporting children bereaved by suicide from Child Bereavement UK.
Thomas Joiner, one of the pre-eminent psychologists working in suicide research today, included a frank and personal account of his experience of losing his own father to suicide interwoven throughout his book Why People Die by Suicide, Harvard University Press, 2005. The book overall is not specifically intended for those bereaved by suicide, but it may be helpful to those who feel that a better understanding of what's known about suicide in general will help them in their recovery.
If you're supporting someone else who's been bereaved by suicide, this guide from the NSPA in the UK might be helpful.