This has worked for me for several years. I wish I could remember who I got it from on the internetz...
I think it was Hitch that mentioned Kindle/Amazon doesn't like Tables, but I'm not sure if "doesn't like" equates to "doesn't work".
I don't use Kindle - except to immediately convert it to ePub.
edit: The technique doesn't actually use "tables" it simply uses the properties of tables in the CSS for "display:table-cell".
You can have any number of items within the inner div and it'll vertically center on the page. Works great for title pages, dedications, Book/Part headings, etc.
Cheers,
Code:
<head>
<title>Vertical Center</title>
<style>
/* Vertically centered on page */
div.v-ctr {height:100%; width:100%; display:table; position:fixed; padding:0; margin:0; text-indent:0}
div.v-ctr div {display:table-cell; vertical-align:middle; padding:0; margin:0}
</style>
</head>
<body>
<div class="v-ctr">
<div>
<p>Centered</p>
</div>
</div>
</body>
</html>