I'm partial to Linode - they're affordable, and performance is top-notch. I've written quite a few articles about them on my blog: <a href="http://sysadminsjourney.com/category/linode">http://sysadminsjourney.com/category/linode</a><br>
<br>You mention security - Linode is a hands-off provider. They give you a VPS, and a distro, and that's about it. Security is up to you. You don't get a CPanel, but you're free to install your own if you like. They also have StackScripts, which allow you to have "click-n-run servers". There's plenty of Drupal StackScripts, check them out at <a href="http://www.linode.com/stackscripts">http://www.linode.com/stackscripts</a>.<br>
<br>Many others are happy with Amazon AWS and Rackspace, but I can't speak for them myself. I have less than stellar personal opinions of running Drupal on Aplus.net and Dreamhost shared hosting.<br><br>HTH,<br><br>Justin<br>