Add link to WebGL playground

index.html

@@ -93,11 +93,12 @@
 
     <ul>
       <li><a href="http://jsbin.com">jsbin.com</a> (JS playground)</li>
-      <li><a href="http://buzzard.ups.edu/">Sage</a> demo (math system)</li>
+      <li><a href="http://buzzard.ups.edu/">Sage demo</a> (math system)</li>
       <li><a href="http://www.sourcelair.com/">sourceLair</a> (online IDE)</li>
       <li><a href="http://eloquentjavascript.net/chapter1.html">Eloquent JavaScript</a> (book)</a></li>
       <li><a href="http://www.mergely.com/">Mergely</a> (interactive diffing)</li>
       <li><a href="http://www.wescheme.org/">WeScheme</a> (learning tool)</li>
+      <li><a href="http://webglplayground.net/">WebGL playground</a></li>
      </ul>
 
   </div></div>