jQuery textarea maxlength for both keypress and paste. Covers lack of "maxlength" attribute in IE. Some credit goes to here: http://stackoverflow.com/questions/6877518/jquery-textarea-maxlength for the keypress section.

textarea-maxlength.js

var ignore = [8,9,13,33,34,35,36,37,38,39,40,46];

$('textarea[maxlength]')
	.live({
	keypress: function(event) {
		var self = $(this),
	  	maxlength = self.attr('maxlength'),
	  	code = $.data(this, 'keycode');
	
	    // check if maxlength has a value.
	    // The value must be greater than 0
	    if (maxlength && maxlength > 0) {
	
		// continue with this keystroke if maxlength
		// not reached or one of the ignored keys were pressed.
		return ( self.val().length < maxlength
	       || $.inArray(code, ignore) !== -1 );
	
	    }
	},
	paste: function() {
		var self = $(this),
		maxlength = self.attr('maxlength');
    	setTimeout(function () {
    		self.val(self.val().substr(0,maxlength));
    	}, 100)
	}
});

I’ve updated it to be more future proof here: https://gist.github.com/jpsirois/4731345