Sometimes you want to store lists in sitecore config files. You could just make a settings and store your values | or , separated. This is not cleanest solutions however, and it makes it hard to add comments to your list elements. Instead you can store your lists in the sitecore config in a clean way.

The first thing you need to do is to create the config file which will store your list. Here's an example of what such a list might look like.

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
  <sitecore>
    <tutorial>
      <cities type="Website.Models.CitiesModel, Website">
        <items hint="list">
          <item>Amsterdam</item>
          <item>Rotterdam</item>
        </items>
      </cities>
    </tutorial>
  </sitecore>
</configuration>

Next you need a model which will contain your list

namespace Website.Models
{
    using System.Collections.Generic;

    public class CitiesModel
    {
        public CitiesModel()
        {
            this.Items = new List<string>();
        }

        public List<string> Items { get; set; }
    }
}

Now you will be able to retrieve your list is an object from for instance a controller

namespace Website.Controllers
{
    using System.Web.Mvc;
    using Website.Models;

    public class YourController : Controller
    {
        public ActionResult Index()
        {
            var cities = Sitecore.Configuration.Factory
                             .CreateObject("tutorial/cities", true) as CitiesModel;

            return this.Content(string.Join(", ", cities.Items));
        }
    }
}

There's more interesting things you can do with the sitecore config. Read more about it here