Typing “rd” by itself does “po [[UIApp keyWindow] recursiveDescription]”, so it dumps your entire on-screen view hierarchy.
Typing “rd someview” does “po [someview recursiveDescription]”, so it dumps the view hierarchy starting at a specific view.
For Mac (Cocoa) apps, the equivalent message is _subtreeDescription, but since a window is not a view, the entire-hierarchy command needs to be “po [[[NSApp frontWindow] contentView] _subtreeDescription]”.
(lldb) po [self.view recursiveDescription]
from one of your view controllers to dump the hierarchy of that view. This of course will work on any object that is a subclass of UIView, such as a UITableView (subclass of UIScrollView, which is in turn a subclass of UIView), a UITableViewCell (directly inherited from UIView), etc.There's a lot of good information provided by Apple on debugging here: http://developer.apple.com/library/ios/#technotes/tn2239/
It's definitely worth the time to go through it all if you spend any time debugging iOS code (and there's a Mac OS X equivalent but I can't speak for its usefulness).
I've also started writing a little piece on debugging code with lldb and Xcode, but it's a work in progress: https://gist.github.com/3943317