Edit in JSFiddle

var slideWidth=300;
var sliderTimer;
$(function(){
$('.slidewrapper').width($('.slidewrapper').children().size()*slideWidth);
    sliderTimer=setInterval(nextSlide,1000);
    $('.viewport').hover(function(){
        clearInterval(sliderTimer);
    },function(){
        sliderTimer=setInterval(prevSlide,1000);
    });
    $('#next_slide').click(function(){
        clearInterval(sliderTimer);
        nextSlide();
        sliderTimer=setInterval(nextSlide,1000);
    });
    $('#prev_slide').click(function(){
        clearInterval(sliderTimer);
        prevSlide();
        sliderTimer=setInterval(nextSlide,1000);
    });
});

function nextSlide(){
    var currentSlide=parseInt($('.slidewrapper').data('current'));
    currentSlide++;
    if(currentSlide>=$('.slidewrapper').children().size())
    {
        $('.slidewrapper').css('left',-(currentSlide-2)*slideWidth);  
        $('.slidewrapper').append($('.slidewrapper').children().first().clone()); 
        $('.slidewrapper').children().first().remove();
        currentSlide--;                        
    }
        $('.slidewrapper').animate({left: -currentSlide*slideWidth},300).data('current',currentSlide);
    
    
}

function prevSlide(){
    var currentSlide=parseInt($('.slidewrapper').data('current'));
    currentSlide--;
    if(currentSlide<0)
    {
        $('.slidewrapper').css('left',-(currentSlide+2)*slideWidth);  
        $('.slidewrapper').prepend($('.slidewrapper').children().last().clone()); 
        $('.slidewrapper').children().last().remove();
        currentSlide++;   
    }
    $('.slidewrapper').animate({left: -currentSlide*slideWidth},300).data('current',currentSlide);
}

<div class='viewport'>
    <ul class='slidewrapper' data-current=0>
        <li class='slide'>
            Slide 1
        </li>
        <li class='slide second'>
            Slide 2
        </li>
        <li class='slide third'>
            Slide 3
        </li>
    </ul>
</div>
<a href='javascript: void(0)' id='prev_slide' class='arrows'>←</a>
<a href='javascript: void(0)' id='next_slide' class='arrows'>→</a>

.viewport{
    width: 300px;
    height: 100px;
    overflow: hidden;
    position: relative;
}
.slidewrapper{
    position: absolute;
    left: 0;
    top: 0;
    height: 100px;
    margin: 0;
    padding: 0;    
}
.slide{
    width: 300px;
    height: 100px;
    float: left;
    list-style: none;
    margin: 0;
    padding: 0;
    background: #ff0000;
}
.second{
     background: #00ff00;   
}
.third{
     background: #0000ff;   
}