in jquery, easily get a cell and work with it as an object.

$.fn.extend({
    getCell:function(r,c){
        return $($(this.find("tr")[r]).find("td")[c]);
    }
});

example:

            //target the 4rth row, 3rd column (array starts at [0])
    var cell = $("#testTable").getCell(3,2);
    var cellText = cell.html();
    cell.html("<a href='http://www.google.com'>"+cellText+"</a>");