How do I list all yanks in emacs?

The list of kills (i.e., the list of things you can yank) is called kill ring and stored in the variable kill-ring, so you can view it (in a not very nice way) with C-h v kill-ring RET.

The kill ring also appears in the menu, under “Edit / Paste from kill menu”. If you use a text mode Emacs or have turned the menu bar off, you can access the menu with M-x tmm-menubar (bound to M-`): type M-` e p followed by the first letter of the item you want to paste (if it's a letter and it's unique, otherwise whatever character is indicated). If you don't want to paste anything, type M-` e p C-g; the kills remain in the *Completions* buffer. The kill texts are displayed truncated to yank-menu-length characters.

To my knowledge, emacs doesn't support that feature out of the box.

If you're using a Debian or Ubuntu Linux distribution, you can install the emacs-goodies-el package, which contains a browse-kill-ring feature (bound to M-y by default).

Alternatively, you can use the browse-kill-ring ELisp package available here.

See also here for a nice article about this problem and other alternate solutions.

EmacsWiki has a satisfying list of solutions. A portable and intuitive solution uses the built-in popup.el to display a vertical list to choose from:

(global-set-key (kbd "C-c y") '(lambda ()
                                 (interactive)
                                 (popup-menu 'yank-menu)))