Plugins
Either use one of the pre-built plugins or build you own, the pre built plugins include Membership, Forum, Newsletter EDM, Permalinks, Twitter & Facebook Login, Geocoder, Create PDF, CSV Import & Export, Exploit Scanner, Website Comments, Report Builder, Outgoing SMS, Email Spam Protector, Auto Backup, Website Saved Searches, Website Favorites, Save & Copy, Shell Console, MySQL Console, QR Code Generator & the list goes on.