keyboard shortcut to jump to the non-whitespace first character in a line
There is no shortcut for it by default. As a hack, you can create ~/Library/KeyBindings/ and save a property list like this as ~/Library/KeyBindings/DefaultKeyBinding.dict:

{
  "~m" = (moveToBeginningOfParagraph:, insertText:, " ", moveLeft:, selectWord:, 
  moveRight:, setMark:, moveToBeginningOfParagraph:, deleteForward:, 
  swapWithMark:, moveLeft:);
}


Then quit and reopen applications to apply the changes. ~m is option-m, which is bound to back-to-indentation in Emacs.

I copied the macro from https://github.com/ttscoff/KeyBindings/blob/master/DefaultKeyBinding.dict. moveToBeginningOfParagraph:, selectWord:, moveRight: would not work with lines that don't start with spaces or tabs. moveToBeginningOfParagraph:,moveWordRight:, moveWordLeft: would not work with some lines where the first non-whitespace character is a special character.

DefaultKeyBinding.dict does not work with some applications like Xcode or Firefox.

See http://www.hcs.harvard.edu/~jrus/site/cocoa-text.html or http://osxnotes.net/keybindings.html for more information.