Note: in emacs terminology, "META" may refer to either "ESC" (which I tend to use), or some combination of ALT/CTRL/??? keys — if you do most of your typing on one keyboard, it may be worth figuring out which combination works for "META". 

Editing, files, and exiting emacs

Default Keystroke(s)	Meaning
^X^C	Save and quit
^X^S, ^Xs	Write file, write all files
^X^W somefile	Write to a new file somefile
^X^F somefile, ^X^V	Start editing a new file called somefile
ESC X revert-buffer	Start editing over, forgetting all changes since last save

Manipulating emacs windows

Default Keystroke(s)	Meaning
^X2, ^X3	Split windows
^Xo	Switch windows
^X^	Make a window larger vertically
^Xb	Switch the current window's buffer

Movement

Default Keystroke(s)	Meaning
^F, ^B, ^N, ^P	The big four: left, down, up, right (←, ↓, ↑, →)
ESC F, ESC B	Forward one word, back one word
^A, ^E	Beginning of current line, end of current line
^V, ESC V	Forward one screen, back one screen
^Ssomething	Incremental search forward for something
ESC x isearch-forward-regexpregexp	Incrementally search forward for regexp (very powerful!)
^Rsomething	Incrementally reverse search for something
ESC >	Go to last line
ESC <	Go to first line
^SPACE	Set mark (start creating a region)
^X^X	Go to mark

Macros

Default Keystroke(s)	Meaning
^X(	Start learning a macro
^X)	End learning a macro
^Xe	Execute a macro

Editing

Default Keystroke(s)	Meaning
^K	"Kill" from this point up to the end of line (saved in "kill" ring)
^O	"Open" a new line immediately below current, "open" a new line immediately above current
^T	"Transpose" the current character and the next one
^W	Cut the current region (saved in "kill" ring)
ESC W	Copy the current region (saved in "kill" ring)
^Y	Paste from latest item in "kill" ring
ESC x query-replace something RET otherthing	Replace something with otherthing
ESC x query-replace-regexp regexp RET otherthing	Replace regexp with otherthing (powerful!)
^Y	Paste from latest item in "kill" ring
ESC x undo	Undo