Script

jQuery(function($){
    $('dd').each(function(){
        var backup = $(this).text();
        $(this).data('backup',backup)
            .click(function(){
            if(!$(this).hasClass('on')){
                $(this).addClass('on');
                var txt = $(this).text();
                $(this).html('<input type="text" value="'+txt+'" />');
                $('dd > input').focus().blur(function(){
                    var inputVal = $(this).val();
                    if(inputVal===''){
                        inputVal = this.defaultValue;
                    };
                    $(this).parent().removeClass('on').text(inputVal);
                });
            };
        });
    });
    $('button').click(function(){;
        $('dd').each(function(){
            var backup = $(this).data('backup');
            $(this).text(backup);
        });
    });
});

HTML

<dl>
    <dt>名前：</dt>
    <dd>技評太郎</dd>

    <dt>会社名：</dt>
    <dd>技術評論社</dd>

    <dt>役職：</dt>
    <dd>WEBディレクター</dd>

    <dt>得意：</dt>
    <dd>jQuery</dd>
</dl>

<button>リセット</button>

Demo