A CodePen by Nick LaDart. Fixed nav hover effect - Testing out a new design concept with a pseudo element hover effect using css-transitions.

index.html

<header class="header" role="banner">
  <h1 class="logo">
    <a href="#">Terence <span>Devine</span></a>
  </h1>
  <div class="nav-wrap">
    <nav class="main-nav" role="navigation">
      <ul class="unstyled list-hover-slide">
        <li><a href="#">About</a></li>
        <li><a href="#">Work</a></li>
        <li><a href="#" class="is-current">Contact</a></li>
        <li><a href="#">Blog</a></li>
      </ul>
    </nav>
    <ul class="social-links list-inline unstyled list-hover-slide">
      <li><a href="#">Twitter</a></li>
      <li><a href="#">Google+</a></li>
      <li><a href="#">GitHub</a></li>
      <li><a href="#">CodePen</a></li>
    </ul>
  </div>
</header>

style.scss

@import "compass";
*, :before, :after{ box-sizing: border-box; }
// FONTS
$sans: 'Source Sans Pro', Helvetica, Arial, sans-serif;

// COLORS
$orange: #77aac7;
$gray: #444;
$gray-shine: #343434;
$white-off: #fff;

// REUSABLE STYLES
.unstyled{ list-style: none; padding: 0; margin: 0;
  a{ text-decoration: none; }
}
.list-inline{ overflow: hidden;
  li{ float: left; }
}

// HEADER STYLES
.header{
  position: fixed;
  left: 0; top: 0; bottom: 0;
  width: 17.5em;
  background: $gray;
}

.logo{
  text-transform: lowercase;
  font: 300 2em $sans;
  text-align: center;
  padding: 0; margin: 0;
  
  a{
    display: block;
    padding: 1em 0;
    color: $white-off;
    text-decoration: none;
    transition: .15s linear color;
    
    &:hover{
      color: #fff;
      span{ color: $orange; }
    }
  }
  
  span{
    font-weight: 700;
    transition: .15s linear color;
  }
}

// MAIN NAV
.main-nav{
  
  ul{
    border-top: solid 1px $gray-shine;
  }
  
  li{
    border-bottom: solid 1px $gray-shine;
  }
  
  a{
    padding: 1.1em 0;
    color: $white-off;
    font: 400 1.125em $sans;
    text:{
      align: center;
      transform: lowercase;
    }
    
    &:hover{
      color: #fff;
    }
  }
}

// SOCIAL LINKS
.social-links{
  border-bottom: solid 1px $gray-shine;
  
  li{
    width: 25%;
    border-left: solid 1px $gray-shine;
    &:first-child{ border: none; }
  }
  
  a{
    display: block;
    height: 5.5em;
    text-align: center;
    color: $gray-shine;
    font: 0.75em/5.5em $sans;
    &:hover{
      color: $white-off;
    }
  }
}

// HOVER SLIDE EFFECT
.list-hover-slide{
  
  li{
    position: relative;
    overflow: hidden;
  }
  
  a{
    display: block;
    position: relative;
    z-index: 1;
    transition: .35s ease color;
    
    &:before{
      content: '';
      display: block;
      z-index: -1;
      position: absolute;
      left: -100%; top: 0;
      width: 100%; height: 100%;
      border-right: solid 5px $orange;
      background: $gray-shine;
      transition: .35s ease left;
    }
    
    &.is-current,
    &:hover{
      
      &:before{
        left: 0;
      }
    }
  }
}