Here is the snippet of how to Create Folder in Document Library programmatically using the Object Model.  It can be used in console applications for loading documents or timer-jobs.

            string spsiteUrl = "http://spdev/";
            string spwebUrl = "forum/";
            string folder = "folder";

            using (SPSite spsite = new SPSite(spsiteUrl))
            {
                using (SPWeb spweb = spsite.OpenWeb(spwebUrl))
                {
                    SPFolder doclibFolder = spweb.Folders["DocLib"]; // Doclib is the URL name of document library
                    SPFolder childFolder = doclibFolder.SubFolders.Add(folder);
                }
            }