C = Control
M = Meta = Alt|Esc

Basics
C-x C-f?"find" file i.e. open/create a file in buffer
C-x C-s?save the file
C-x C-w?write the text to an alternate name
C-x C-v?find alternate file
C-x i?insert file at cursor position
C-x b?create/switch buffers
C-x C-b?show buffer list
C-x k?kill buffer
C-z?suspend emacs?
C-X C-c?close down emacs

Basic movement
C-f?forward char
C-b?backward char
C-p?previous line
C-n?next line
M-f?forward one word
M-b?backward one word
C-a?beginning of line
C-e?end of line
C-v?one page up
M-v?scroll down one page
M-<?beginning of text
M->?end of text

Editing
M-n?repeat the following command n times
C-u?repeat the following command 4 times
C-u n?repeat n times
C-d?delete a char
M-d?delete word
M-Del?delete word backwards
C-k?kill line

C-Space?Set beginning mark (for region marking for example)
C-W?"kill" (delete) the marked region region
M-W?copy the marked region
C-y?"yank" (paste) the copied/killed region/line
M-y?yank earlier text (cycle through kill buffer)
C-x C-x?exchange cursor and mark

C-t?transpose two chars
M-t?transpose two words
C-x C-t?transpose lines
M-u?make letters uppercase in word from cursor position to end
M-c?simply make first letter in word uppercase
M-l?opposite to M-u

Important
C-g?quit the running/entered command
C-x u?undo previous action
M-x revert-buffer RETURN?(insert like this) undo all changes since last save
M-x recover-file RETURN?Recover text from an autosave-file
M-x recover-session RETURN?if you edited several files

Online-Help
C-h c?which command does this keystroke invoke
C-h k?which command does this keystroke invoke and what does it do?
C-h l?what were my last 100 typed keys
C-h w?what key-combo does this command have?
C-h f?what does this function do
C-h v?what‘s this variable and what is it‘s value
C-h b?show all keycommands for this buffer
C-h t?start the emacs tutorial
C-h i?start the info reader
C-h C-k?start up info reader and go to a certain key-combo point
C-h F?show the emacs FAQ
C-h p?show infos about the Elisp package on this machine

Search/Replace
C-s?Search forward
C-r?search backward
C-g?return to where search started (if you are still in search mode)
M-%?query replace

Space or y?replace this occurence
Del or n?don‘t replace
.?only replace this and exit (replace)
,?replace and pause (resume with Space or y)
!?replace all following occurences
^?back to previous match
RETURN or q?quit replace

Search/Replace with regular expressions
Characters to use in regular expressions:
^?beginning of line
$?end of line
.?single char
.*?group or null of chars
\<?beginning of a word
\>?end of a word
[]?every char inside the backets (for example [a-z] means every small letter)

M C-s RETURN?search for regular expression forward
M C-r RETURN?search for regular expression backward
M C-s?incremental search
C-s?repeat incremental search
M C-r?incremental search backwards
C-r?repeat backwards
M-x query-replace-regexp?search and replace

Window-Commands
C-x 2?split window vertically
C-x o?change to other window
C-x 0?delete window
C-x 1?close all windows except the one the cursors in
C-x ^?enlarge window
M-x shrink-window?command says it ;-)
M C-v?scroll other window
C-x 4 f?find file in other window
C-x 4 o?change to other window
C-x 4 0?kill buffer and window
C-x 5 2?make new frame
C-x 5 f?find file in other frame
C-x 5 o?change to other frame
C-x 5 0?close this frame

Bookmark commands
C-x r m?set a bookmark at current cursor pos
C-x r b?jump to bookmark
M-x bookmark-rename?says it
M-x bookmark-delete?"
M-x bookmark-save?"
C-x r l?list bookmarks

d?mark bookmark for deletion
r?rename bookmark
s?save all listed bookmarks
f?show bookmark the cursor is over
m?mark bookmarks to be shown in multiple window
v?show marked bookmarks (or the one the cursor is over)
t?toggle listing of the corresponding paths
w?" path to this file
x?delete marked bookmarks
Del??
q?quit bookmark list

M-x bookmark-write?write all bookmarks in given file
M-x bookmark-load?load bookmark from given file

Shell
M-x shell?starts shell modus
C-c C-c?same as C-c under unix (stop running job)
C-d?delete char forward
C-c C-d?Send EOF
C-c C-z?suspend job (C-z under unix)
M-p?show previous commands

DIRectory EDitor (dired)
C-x d?start up dired
C?(large C) copy?
d?mark for erase
D?delete right away
e or f?open file or directory
g?reread directory structure from file
G?change group permissions (chgrp)
k?delete line from listing on screen (don‘t actually delete)
m?mark with *
n?move to next line
o?open file in other window and go there
C-o?open file in other window but don‘t change there
P?print file
q?quit dired
Q?do query-replace in marked files
R?rename file
u?remove mark
v?view file content
x?delete files marked with D
z?compress file
M-Del?remove all marks (whatever kind)
~?mark backup files (name~ files) for deletion
#?mark auto-save files (#name#) for deletion
*/?mark directory with * (C-u * removes that mark again)
=?compare this file with marked file
M-=?compare this file with it‘s backup file
!?apply shell command to this file
M-}?change to the next file marked with * od D
M-{?" previous "
% d?mark files described through regular expression for deletion
% m?" (with *)
+?create directory
>?changed to next dir
<?change to previous dir
s?toggle between sorting by name or date

Maybe into this category also fits this command:
M-x speedbar?starts up a separate window with a directory view

Telnet
M-x telnet?starts up telnet-modus
C-d?either delete char or send EOF
C-c C-c?stop running job (similar to C-c under unix)
C-c C-d?send EOF
C-c C-o?clear output of last command
C-c C-z?suspend execution of command
C-c C-u?kill line backwards
M-p?recall previous command

Text
Works only in text mode?
M-s?center line
M-S?center paragraph
M-x center-region?name says?

Macro-commands
C-x (?start macro definition
C-x )?end of macro definition
C-x e?execute last definied macro
M-n C-x e?execute last defined macro n times
M-x name-last-kbd-macro?give name to macro (for saving)
M-x insert-keyboard-macro?save named macro into file
M-x load-file?load macro
M-x macroname?execute macroname

Programming
M C-\?indent region between cursor and mark
M-m?move to first (non-space) char in this line
M-^?attach this line to previous
M-;?formatize and indent comment
C, C++ and Java Modes
M-a?beginning of statement
M-e?end of statement
M C-a?beginning of function
M C-e?end of function
C-c RETURN?Set cursor to beginning of function and mark at the end
C-c C-q?indent the whole function according to indention style
C-c C-a?toggle modus in which after electric signs (like {}:‘;./*) emacs does the indention
C-c C-d?toggle auto hungry mode in which emacs deletes groups of spaces with one del-press
C-c C-u?go to beginning of this preprocessor statement
C-c C-c?comment out marked area
More general (I guess)
M-x outline-minor-mode?collapses function definitions in a file to a mere {...}?
M-x show-subtree?If you are in one of the collapsed functions, this un-collapses it?
In order to achive some of the feats coming up now you have to run etags *.c *.h *.cpp (or what ever ending you source files have) in the source directory
M-.?(Thats Meta dot) If you are in a function call, this will take you to it‘s definition?
M-x tags-search ENTER?Searches through all you etaged?
M-,?(Meta comma) jumps to the next occurence for tags-search?
M-x tags-query-replace?yum. This lets you replace some text in all the tagged files?


GDB (Debugger)
M-x gdb?starts up gdm in an extra window

Version Control
C-x v d?show all registered files in this dir
C-x v =?show diff between versions
C-x v u?remove all changes since last checkin
C-x v ~?show certain version in different window
C-x v l?print log
C-x v i?mark file for version control add
C-x v h?insert version control header into file
C-x v r?check out named snapshot
C-x v s?create named snapshot
C-x v a?create changelog file in gnu-style

Emacs Commands List