List<Post> posts = GetPosts();
 
JObject rss = 
  new JObject(
    new JProperty("channel",
      new JObject(
        new JProperty("title", "James Newton-King"),
        new JProperty("link", "http://james.newtonking.com"),
        new JProperty("description", "James Newton-King's blog."),
        new JProperty("item",
          new JArray(
            from p in posts
            orderby p.Title
            select new JObject(
              new JProperty("title", p.Title),
              new JProperty("description", p.Description),
              new JProperty("link", p.Link),
              new JProperty("category",
                new JArray(
                  from c in p.Categories
                  select new JValue(c)))))))));

{
  "channel": {
    "title": "James Newton-King",
    "link": "http://james.newtonking.com",
    "description": "James Newton-King's blog.",
    "item": [
      {
        "title": "Json.NET 1.3 + New license + Now on CodePlex",
        "description": "Annoucing the release of Json.NET 1.3,...",
        "link": "http://james.newtonking.com/projects/json-net.aspx",
        "category": [
          "Json.NET",
          "CodePlex"
        ]
      },
      {
        "title": "LINQ to JSON beta",
        "description": "Annoucing LINQ to JSON",
        "link": "http://james.newtonking.com/projects/json-net.aspx",
        "category": [
          "Json.NET",
          "LINQ"
        ]
      }
    ]
  }
}