Where To Put Page-specific JavaScript

I have a little menu system which essentially takes HTML like:

<div id='foo'></div>

and retrieves foo.shtml from the server and inserts it inside the
<div>. But sometimes I'd like foo.shtml to look like:

<script language='JavaScript'>
...do something AJAX-y
</script>
<div></div>

so that the script fills in the page. I've hacked together something
that inserts the foo.shtml into foo's div then does a
fooDiv.getElementsByTagName('script') and uses eval() on them and it
works most of the time in some brossers but it seems hackish and
somewhat dangerous and it doesn't work everywhere. Surely there's an
AJAX idiom (or even a DOM built-in) to execute scripts as parts of
pages load.