jQuery replaceText will replace text in specified elements. Note that only text content will be modified, leaving all tags and attributes untouched.

/*!
 * jQuery replaceText - v1.2 - 11/13/2013
 * http://benalman.com/projects/jquery-replacetext-plugin/
 * Created from https://github.com/WalrusCow/jquery-replacetext/commit/67b653339b31f86a4cbf5fbf2873d5976128bc5d
 * Pull request: https://github.com/cowboy/jquery-replacetext/pull/5
 *
 * Copyright (c) 2009 "Cowboy" Ben Alman
 * Dual licensed under the MIT and GPL licenses.
 * http://benalman.com/about/license/
 */

// Script: jQuery replaceText: String replace for your jQueries!
//
// *Version: 1.2, Last updated: 11/13/2013*
//
// Project Home - http://benalman.com/projects/jquery-replacetext-plugin/
// GitHub       - http://github.com/cowboy/jquery-replacetext/
// Source       - http://github.com/cowboy/jquery-replacetext/raw/master/jquery.ba-replacetext.js
// (Minified)   - http://github.com/cowboy/jquery-replacetext/raw/master/jquery.ba-replacetext.min.js (0.5kb)
//
// About: License
//
// Copyright (c) 2009 "Cowboy" Ben Alman,
// Dual licensed under the MIT and GPL licenses.
// http://benalman.com/about/license/
//
// About: Examples
//
// This working example, complete with fully commented code, illustrates one way
// in which this plugin can be used.
//
// replaceText - http://benalman.com/code/projects/jquery-replacetext/examples/replacetext/
//
// About: Support and Testing
//
// Information about what version or versions of jQuery this plugin has been
// tested with, and what browsers it has been tested in.
//
// jQuery Versions - 1.3.2, 1.4.1
// Browsers Tested - Internet Explorer 6-8, Firefox 2-3.6, Safari 3-4, Chrome, Opera 9.6-10.1.
//
// About: Release History
//
// 1.2 - (11/13/2013) Maintain escaped HTML entities.
// 1.1 - (11/21/2009) Simplified the code and API substantially.
// 1.0 - (11/21/2009) Initial release

(function ($) {
    // Method: jQuery.fn.replaceText
    //
    // Replace text in specified elements. Note that only text content will be
    // modified, leaving all tags and attributes untouched. The new text can be
    // either text or HTML.
    //
    // Uses the String prototype replace method, full documentation on that method
    // can be found here:
    //
    // https://developer.mozilla.org/En/Core_JavaScript_1.5_Reference/Objects/String/Replace
    //
    // Usage:
    //
    // > jQuery('selector').replaceText( search, replace [, text_only ] );
    //
    // Arguments:
    //
    //  search - (RegExp|String) A RegExp object or substring to be replaced.
    //    Because the String prototype replace method is used internally, this
    //    argument should be specified accordingly.
    //  replace - (String|Function) The String that replaces the substring received
    //    from the search argument, or a function to be invoked to create the new
    //    substring. Because the String prototype replace method is used internally,
    //    this argument should be specified accordingly.
    //  text_only - (Boolean) If true, any HTML will be rendered as text. Defaults
    //    to false.
    //
    // Returns:
    //
    //  (jQuery) The initial jQuery collection of elements.

    // Map to escape HTML entities
    var entityMap = {
        escape: {
            '>': '>',
            '<': '&lt;',
            '"': '&quot;',
            "'": '&#x27;',
            '&': '&amp;'
        },
        unescape: {} // We will set this below
    };

    // We will use these arrays to build regular expressions for escaping
    var unescapedChars = [],
        escapedChars = [];

    for (key in entityMap.escape) {
        // Add an inverted `unescape` object to unescape HTML
        entityMap.unescape[entityMap.escape[key]] = key;

        // Track both the escaped and unescaped versions
        unescapedChars.push(key);
        escapedChars.push(entityMap.escape[key]);
    }

    // Build regular expressions to escape with
    var entityRegex = {
        escape: new RegExp('[' + unescapedChars.join('') + ']', 'g'),
        unescape: new RegExp('(' + escapedChars.join('|') + ')', 'g')
    };

    // Generically escape or unescape HTML entities in the code
    function esc(str, method) {
        // Nothing to do with null or empty string
        if (!str) {
            return str;
        }

        // Replace proper strings with their corresponding replacements
        return str.replace(entityRegex[method], function (match) {
            return entityMap[method][match];
        });
    }

    function escapeHtml(str) {
        return esc(str, 'escape');
    }

    function unescapeHtml(str) {
        return esc(str, 'unescape');
    }

    $.fn.replaceText = function (search, replace, textOnly) {
        return this.each(function () {
            var node = this.firstChild,
                val,
                newVal,

                // Elements to be removed at the end.
                remove = [];

            // Only continue if firstChild exists.
            if (node) {

                // Loop over all childNodes.
                do {

                    // Only process text nodes.
                    if (node.nodeType === 3) {

                        // The original node value.
                        // We need to escape existing HTML because `nodeValue` unescapes
                        // escaped HTML values.
                        val = escapeHtml(node.nodeValue);

                        // The new value.
                        newVal = val.replace(search, replace);

                        // Only replace text if the new value is actually different!
                        if (newVal !== val) {

                            if (!textOnly && (/</).test(newVal)) {
                                // The new value contains HTML, set it in a slower but far more
                                // robust way.
                                $(node).before(newVal);

                                // Don't remove the node yet, or the loop will lose its place.
                                remove.push(node);
                            }
                            else {
                                // The new value contains no HTML, so it can be set in this
                                // very fast, simple way.
                                // We need to unescape the HTML now, because we previously
                                // escaped it.
                                node.nodeValue = unescapeHtml(newVal);
                            }
                        }
                    }

                } while (node = node.nextSibling);
            }

            // Time to remove those elements!
            remove.length && $(remove).remove();
        });
    };
})(jQuery);