WPF ListBox that lays out its items horizontally

WrapPanel

 <ListBox ScrollViewer.HorizontalScrollBarVisibility="Disabled">
    <ListBox.ItemsPanel>
        <ItemsPanelTemplate>
            <WrapPanel IsItemsHost="True" />
        </ItemsPanelTemplate>
    </ListBox.ItemsPanel>
    <ListBoxItem>listbox item 1</ListBoxItem>
    <ListBoxItem>listbox item 2</ListBoxItem>
    <ListBoxItem>listbox item 3</ListBoxItem>
    <ListBoxItem>listbox item 4</ListBoxItem>
    <ListBoxItem>listbox item 5</ListBoxItem>
</ListBox>

WPF Tutorial