I’ve been wanting to experiment with HTML5 to see how far it has come.  So my tentative plan is to use Inkscape as my primary art/design tool with GIMP for supplemental sprite processing.  I’ll be writing Javascript / HTML / CSS in Emacs.  I don’t want to kill too much time digging around foreign libraries for this, but will probably try to make use of jQuery along with (possibly:) a box2d port and raphael(?).  I know this is probably a lot to bite off in one weekend, but look forward to the challenge!  You can follow my progress through my blog: http://sugarpillstudios.com and on twitter @SugarPillStdios.