A while ago, I was discussing one way to avoid the need to register for every site.
Here's another, geared towards those pesky sites that require an email to register or get a download link.
Guerrilla Mail will give you a temporary email address, good for 15 minutes (can be extended further, if needed). Just specify that on the registration form, log into the mailbox from the site and collect the information you need.
Great idea. Simple and clean interface. Now can someone please give an disposable mailbox I can SEND email from? :)