Well, first of all, you aren't really using basic JavaScript when you do that.
You are using the jQuery library. So some of the code is going to be a bit (or a LOT!) different than if you were using ordinary JavaScript.
It is kind of like you are using a GPS navigation system (e.g, a TomTom or similar) but never learned how to read a map. You are trusting that your navigation system will always know how to read the map for you.
But to directly answer your question:
Code:
<script type="text/javascript">
$(document).ready(function() {
$('.slideshowA').cycle({
fx: 'fade',
speed: 4000,
delay: 0
});
$('.slideshowB').cycle({
fx: 'fade',
speed: 4000,
delay: -1000
});
$('.slideshowC').cycle({
fx: 'fade',
speed: 4000,
delay: -2000
});
});
</script>
I don't think you an make it much shorter than that without major changes to how you code it.