Emacs equivalents of Vim's dd,o,O

For o and O, here are a few functions I wrote many years ago:

(defun vi-open-line-above ()
  "Insert a newline above the current line and put point at beginning."
  (interactive)
  (unless (bolp)
    (beginning-of-line))
  (newline)
  (forward-line -1)
  (indent-according-to-mode))

(defun vi-open-line-below ()
  "Insert a newline below the current line and put point at beginning."
  (interactive)
  (unless (eolp)
    (end-of-line))
  (newline-and-indent))

(defun vi-open-line (&optional abovep)
  "Insert a newline below the current line and put point at beginning.
With a prefix argument, insert a newline above the current line."
  (interactive "P")
  (if abovep
      (vi-open-line-above)
    (vi-open-line-below)))

You can bind vi-open-line to, say, M-insert as follows:

(define-key global-map [(meta insert)] 'vi-open-line)

For dd, if you want the killed line to make it onto the kill ring, you can use this function that wraps kill-line:

(defun kill-current-line (&optional n)
  (interactive "p")
  (save-excursion
    (beginning-of-line)
    (let ((kill-whole-line t))
      (kill-line n))))

For completeness, it accepts a prefix argument and applies it to kill-line, so that it can kill much more than the "current" line.

You might also look at the source for viper-mode to see how it implements the equivalent dd, o, and O commands.

C+e C+j

According to the emacs manual docs. That gets you a new line and indentation.

For dd, use "kill-whole-line", which is bound to "C-S-backspace" by default in recent versions of Emacs.

I should add that I myself use whole-line-or-region.el more often, since C-w is easier to type than C-S-backspace.