General/UIKit is the UI framework in the General/IPhoneRuntime, the equivalent of General/AppKit for traditional OS X apps. Most of the classes are more or less equivalent to their NS- prefixed General/AppKit counterparts.
Warning: The information listed here may be incomplete, incorrect, or extremely misleading. If in doubt, wait until the official SDK is released.
** Useful classes: **
*General/UIHardware: information about the device *General/UIApplication: main application class
*General/UIWindow *General/UIResponder *General/UIView *General/UIControl *General/UIImage *General/UIImageView
*General/UINavigationBar: That swank little bar at the top with a button or two *General/UIButtonBar *General/UITextView *General/UITextLabel *General/UITextField *General/UIKeyboard: The iPhone’s keyboard *General/UIFontChooser *General/UISegmentedControl *General/UISliderControl *General/UISwitchControl: On/Off switch *General/UIPickerView *General/UIPushButton *General/UIAlertSheet *General/UITransitionView *General/UIProgressHUD
*General/UITable: iPhone’s list UI. Related classes:
*General/UITableColumn *General/UITableCell *General/UIImageAndTextTableCell *General/UIPreferencesTable *General/UIPreferencesTableCell *General/UISectionList
*General/UIAnimation
For General/UIKit tips and tricks, check out slerp: http://phonedev.tumblr.com