And there's this, too: Ellipsifier is a Javascript library that truncates HTML. It will retain the tag structure, counting only visible characters in the resulting text.

new Ellipsifier("to be or not to be", 5).result
//              "to be …"
new Ellipsifier('to <strong>be or</strong> not to be', 20).result
//              "to <strong>be or</strong> not to be"
new Ellipsifier('to <strong>be or</strong> not to be', 5).result
//              "to <strong>be</strong>&nbsp;&hellip;"

Another chunk of code written with the good folks at HowAboutWe.