Are you looking for something like this?

<ul>
        @foreach (var rootCategory in categoryList)
        {
            <li><a href="@rootCategory.GetNiceUrl()">@rootCategory.Name</a>
                @if (rootCategory.Categories.Any())
                {
                    <ul>
                        @foreach (var subCategories in rootCategory.Categories.Where(x => x.DisplayOnSite))
                        {
                            <li><a href="@subCategories.GetNiceUrl()">@subCategories.Name</a>
                                <ul>
                                    @foreach (var subsubCategories in subCategories.Categories.Where(x => x.DisplayOnSite))
                                    {
                                        <li><a href="@subsubCategories.GetNiceUrl()">@subsubCategories.Name</a>
                                        </li>
                                    }
                                </ul>
                            </li>
                        }
                    </ul>
                }
            </li>
        }
    </ul>

im looking for a menu that only show categories in level one.
when click on them the meny fold out the subcategories on the one you click...

You could go with the CSS hover version:

http://www.htmldog.com/articles/suckerfish/dropdowns/

Else you need a javascript to hide and show child list on click.

(lots of google examples on both).

is working on a reply...