I'd agree that you're likely to end up having your email address distributed when signing up for something like this.
My preference, in order:
1) A disposable address, as suggested by Karrax. These domains are often blocked, unfortunately.
2) If you have the ability though a non-free mail address, add an alias. That way you can delete it when you no longer need it, or when it starts to get spam, but until then, you can still receive confirmation emails and the like.
3) A dedicated web email address. This is an email address that you use whenever you need to sign up on the web, you check when you know you have a confirmation email or download link, and just ignore the spam that it collects the rest of the time.
4) The GMail style +suffix. I don't like this option as well, because it exposes your real email address to anybody who's interested in looking, but it's better than nothing.
I hope this helps,