Many poets and writers have described their suicidal feelings. Leo Tolstoy, for instance.
Tolstoy passed through a suicidal crisis before his religious conversion at about the age of 50, and described it in My Confession. It is curious that he describes himself as both happy and healthy and yet suicidal, but that is just one of the paradoxical features of depression:

"The truth lay in this – that life had no meaning for me. Every day of life, every step in it, brought me nearer to the edge of a precipice, whence I saw clearly the final ruin before me. To stop, to go back, were alike impossible; nor could I shut my eyes so as to not see the suffering that alone awaited me, the death of all in me even to annihilation. Thus I, a healthy and happy man, was brought to feel that I could live no longer, that an irresistible force was dragging me down into the grave. I do not mean that I had an intention of committing suicide. The force that drew me away from life was stronger, fuller, and concerned with far wider consequences than any mere wish; it was a force like that of my previous attachment to life, only in a contrary direction. The idea of suicide came as naturally to me as formerly bettering my life. It had so much attraction for me that I was compelled to practice a species of self-deception, in order to avoid carrying it out too hastily. I was unwilling to act hastily, only because I had determined first to clear away the confusion of my thoughts, and, once that done, I could always kill myself. I was happy, yet I hid away a cord, to avoid being tempted to hang myself by it to one of the pegs between the cupboards of my study, where I undressed alone every evening, and ceased carrying a gun because it offered too easy a way of getting rid of life. I knew not what I wanted; I was afraid of life, and yet there was something I hoped for from it."

Freud tackled the task of theorizing the explanations for suicide in Mourning and Melancholia:

So immense is the ego’s self-love, which we have come to recognise as the primal state from which instinctual life proceeds, and so vast is the amount of narcissistic libido which we see liberated in the fear that emerges as a threat to life, that we cannot conceive how the ego can consent to its own destruction. We have long known, it is true, that no neurotic harbours thoughts of suicide which he has not turned back upon himself from murderous impulses against others, but we have never been able to explain what interplay of forces can carry such a purpose through to execution. The analysis of melancholia now shows that the ego can kill itself only if, owing to the return of the object-cathexis, it can treat itself as an object – if it is able to direct against itself the hostility which relates to an object and which represents the ego’s original reaction to objects in the external world. Thus in regression from narcissistic object choice the object has, it is true, been got rid of, but it has nevertheless proved more powerful than the ego itself,. In the two most opposed situations of being most intensely in love and of suicide the ego is overwhelmed by the object, though in totally different ways.

But is it really reasonable to accept that self-love of the ego is a primal state and that suicidal thoughts always reflect murderous thoughts towards others? To find evidence to support such views we really must further examine the psychological basis of depression.

There are a lot of suicide related nodes on Everything2. I thought I'd put them all together.

People who committed suicide:

Suicide Notes:

Personal propensity towards suicide, experiences and opinions:

The Facts:

Methods of suicide:

Songs and poems about suicide:

Movies about suicide:

Books about suicide, or with suicide in them:

Help, support and advice for suicidal people:

Everything suicide

Other miscellanous 'forms' of suicide: (things with suicide in their name, etc)