SP: export/import ctypes and fields PS

Export and import/create site columns in SharePoint using PowerShell
http://get-spscripts.com/2011/01/export-and-importcreate-site-columns-in.html

Export and import/create site content types in SharePoint using PowerShell
http://get-spscripts.com/2011/02/export-and-importcreate-site-content.html