Edit in JSFiddle

@import url(http://fonts.googleapis.com/css?family=Alef);
* {margin: 0; padding: 0; border: 0 none;}

html {
    padding: 2rem;
    background: #044C62;
    color: #7CD7C4;
    font-family: 'Alef', sans-serif;
}
body {
    background: #F57B6C;
    padding: 2rem;
}
.contenedor {
    padding: 2rem;
    height: 100px;
    background:  #4788B0;
}
.max {
    display: inline-block;
    width: 40%;
    margin-right: 9%;
    height: 100%;
    vertical-align: top;
}
.b {
    background: #044C62;
    border-radius: 3px;
    display: inline-block;
    text-decoration: none;
    font-size: 1.5rem;
    padding: 0 1.5rem 0 .5rem;
    overflow: hidden;  
    color: #7CD7C4;
    max-width: 0;
    -moz-transition: 2s linear; 
    -webkit-transition: 2s linear; 
    transition: 2s linear; 
}
.b:hover{
    max-width: 500px;
}
.b:before {
    content: '\25BA';
    position: relative;   
    color: #fff;
    padding: 0 1rem 0 0;
    color: inherit;
    font-weight: 900;
}
.menu {
    overflow: hidden;
    cursor: pointer;
}
h3 {
    background: #044C62;
    border-radius: 3px;
}
.redes {
    background: #044C62;
    max-height: 0;
    -moz-transition: max-height 2s linear;
    -webkit-transition: max-height 2s linear;
    transition: max-height 2s linear;
}
.menu li:hover .redes {
    max-height: 500px;
    color: #E8EEE7;
}
.redes li:hover {background: #F57B6C;}

<div class="contenedor">
   <div class="max">
    <p>Max-height</p>
    <ul class="menu">
        <li><h3>Redes</h3>
            <ul class="redes">
                <li>En Gplus</li>
                <li>En Twitter</li>
                <li>En Blogger</li>
            </ul>
        </li>
       </ul>
   </div>
   <div class="max">
    <p>Max-width</p>
    <a class="b" href="">KsesoCss</a>
   </div>
</div>