Specific html within wordpress loop

Use rewind_posts() to reset a loop and run it multiple times:

<?php

$my_query = new WP_Query('cat=49&showposts=4&orderby=RAND');
?>
<div id="carousel">
<?php
while ($my_query->have_posts()) : $my_query->the_post();
    // output each slide
endwhile;
?>
</div>
<?php

$my_query->rewind_posts();
?>
<ul id="carousel-descriptions">
<?php
while ($my_query->have_posts()) : $my_query->the_post();
    // output each desc
endwhile;
?>
</ul>
<?php

$my_query->rewind_posts();
// etc.