Version:            (using KDE KDE 3.3.1)
Installed from:    SuSE RPMs
OS:                Linux

According to XDND, when drag & dropping, a TARGETS Atom listing all available targets (as a list of other Atom s, generally named after their mime type) is provided.
But, nothing is provided.
Here is how I get targets, using Gtk/Gdk; this works with Gtk, Mozilla, and Motif; but outputs only null strings with KDE.

//in a drag-drop signal handler

  GtkClipboard *cboard =
	gtk_clipboard_get(gdk_drag_get_selection(drag_context));

    gtk_clipboard_request_targets(cboard, print_received_targets, NULL);
//Try it another way:
gtk_clipboard_request_contents(cboard, gdk_atom_intern("TARGETS", FALSE), print_data_from_clipboard, NULL);

//With:
void print_data_from_clipboard(GtkClipboard * clipboard,
			       GtkSelectionData * selection_data,
			       gpointer data)
{
    g_printf("print_data_from_clipboard\n");
    print_gtk_selection_data(selection_data);
}

//And:
void print_gtk_selection_data(GtkSelectionData * seldat)
{
    gchar *as_text = gtk_selection_data_get_text(seldat);
    if (as_text) {
	g_printf("As utf-8 text: %s\n", as_text);
	g_free(as_text);
    }
    g_printf("As raw bytes:\n");

    int i;
    for (i = 0; i < seldat->length; i++) {
	g_printf("%c", seldat->data[i]);
    }
    g_printf("\n");
}