There's already a billion of these out there, but I thought I'd make mine aswell.. This one is coded in javascript / html..
I made two version of them, as I thought.. Both may come in handy for someone, I don't know
First one is like most programs. You click generate and it gives you a key.
Second one is a bit more uhmm.. Advanced? You can type in how many keys you want generated, and it'll create them in an easy copy-paste format..
Enjoy! 
Code for the first one (1 gen pr. click):
Code:
<html>
<head>
<script type='text/javascript'>
function generate() {
code = '';
for(i=0; i<4; i++) {
code = code + Math.round(Math.random()*9);
}
code = code+'-';
for(i=0; i<6; i++) {
code = code + Math.round(Math.random()*9);
}
code = code+'-';
for(i=0; i<5; i++) {
code = code + Math.round(Math.random()*9);
}
code = code+'-';
for(i=0; i<6; i++) {
code = code + Math.round(Math.random()*9);
}
code = code+'-';
for(i=0; i<4; i++) {
code = code + Math.round(Math.random()*9);
}
document.getElementById('keyfield').value = code
}
</script>
</head>
<body>
<center>
<input type=text id='keyfield' size=40 style='text-align: center;'><br>
<input type=button value='Generate!' onClick='generate()'>
</center>
</body>
</html>
And the second one(Type amount of keys to generate):
Code:
<html>
<head>
<script type='text/javascript'>
function mass() {
document.getElementById('massContainer').innerHTML = '';
times = document.getElementById('times').value;
a=0;
while(a<times) {
generate();
a++;
}
}
function generate() {
code = '';
for(i=0; i<4; i++) {
code = code + Math.round(Math.random()*9);
}
code = code+'-';
for(i=0; i<6; i++) {
code = code + Math.round(Math.random()*9);
}
code = code+'-';
for(i=0; i<5; i++) {
code = code + Math.round(Math.random()*9);
}
code = code+'-';
for(i=0; i<6; i++) {
code = code + Math.round(Math.random()*9);
}
code = code+'-';
for(i=0; i<4; i++) {
code = code + Math.round(Math.random()*9);
}
document.getElementById('massContainer').innerHTML = document.getElementById('massContainer').innerHTML + code + "<br />"
}
</script>
</head>
<body>
<center>
<input type=text value='1' size=3 id='times'>
<input type=button value='Generate!' onClick='mass()'><br />
<div id='massContainer'>
</div>
</center>
</body>
</html>
Enjoy! =D
PS. I only used 2-3 minutes on this, so there's no whitespace and uhmm.. Yeah, but it works ^_^