Frameworks to look into

AddressBook
AppKit
AudioToolBox
ApplicationServices
Automator
CalendarStore
Cocoa
CoreAudio
CoreFoundation
CoreLocation
CoreMotion
DirectoryService
EventKit
Foundation
GSS
iAd
ImageIO
InstantMessage
IOKit
Kernal
LDAP -> OpenDirectory
Message
PreferencePanes
QuickLook
SceneKit
ScreenSaver
Scripting (deprecated?)
Security
ServerNotification
PubSub (RSS/Atom support!)
StoreKit
SyncServices