Hello, I finally figured out how to update the categories for a single blog entry by using this:

    [WebMethod]
    public string Update(int postId, string stuff)
    {
        var cs = ApplicationContext.Current.Services.ContentService;
        var post = cs.GetById(postId);
        post.SetValue("categories", stuff);
        var status = cs.SaveAndPublishWithStatus(post);

        return string.Format("updated post id {0}", post.Id);
    }

How can I get a list of all Articulate blog entries (or even a filtered subset) and use a foreach loop to update the categories/tags by calling post.SetValue("categories", stuff)?

Kind regards.