+ 0) $DISPLAY parser
+ 0.1) basic connection setup, tcp/unix socket, unix/win
+ 1) x11 core protocol parser: handshake (no auth), request, reply, events, errors. Requests, replies and events queues.
+ 2) handwritten basic requests: CreateWindow, MapWindow, basic GC, simple examples

3) extensions support
3.5) XRender examples, FreeType or Xft wrapper (native module? ffi? https://github.com/rbranson/node-ffi/ http://www.freetype.org/freetype2/docs/tutorial/step1.html example)

4) tool to automatically generate requests from xcb xml description http://xcb.freedesktop.org/XmlXcb/ http://cgit.freedesktop.org/xcb/proto/tree/src?id=HEAD
( https://github.com/CrypticSwarm/XCBJS )

+ 5) authorisation
6) examples: js implementation for basic X utilities: xev, xeyes, xclock, xclip, xauth, xkill, xlsatoms, glxgears etc.
_7) vnc client using https://github.com/substack/node-rfb
8) rdesktop client using https://github.com/substack/node-rdesktop
9) widget implementing basic subset of html5 canvas api using https://github.com/learnboost/node-canvas or https://github.com/ajaxorg/node-o3-canvas
10) pdf viewer using https://github.com/andreasgal/pdf.js/, (ODF viewer? - http://webodf.org/demo/)
12) ICCCM library http://www.x.org/docs/ICCCM/icccm.pdf http://tronche.com/gui/x/icccm/
+11) pure js window manager
12) general purpose widgets set, layout managers, box model
13) pure js web browser :)