HTML: http://www.w3.org/TR/html4/ http://www.sitepoint.com/books/html1/
CSS: http://www.sitepoint.com/books/cssdesign1/ http://www.css-discuss.org/
JS:
See this timeless rant for a tiny example (countering all the bad advice you see on a trivially easy feature): http://youngpup.net/archived/popups.html
You may wish to do some JS dev without a framework just to get a taste for the terrible truth. Then get jquery or one of the other excellent tools.
JS quirks: http://www.quirksmode.org/
Books: http://www.amazon.com/JavaScript-Good-Parts-Douglas-Crockfor... http://www.amazon.com/Pro-JavaScript-Techniques-John-Resig/d...
Also, some good tools: wget curl firebug wireshark (neé ethereal) yslow
webby python code libs: http://codespeak.net/lxml/ http://code.google.com/p/httplib2/ http://code.google.com/p/simplejson/ http://labix.org/python-dateutil
Relevant validators: http://validator.w3.org/ http://www.jslint.com/ http://jigsaw.w3.org/css-validator/ http://feedvalidator.org/
http://www.amazon.com/Pro-JavaScript-Techniques-John-Resig/d...