I have my domains hooked up with google apps (there was a time when it was free, still is if you got in early), and they allow you to have a catch-all for email

I have my domains hooked up with google apps (there was a time when it was free, still is if you got in early), and they allow you to have a catch-all for email addresses that you can redirect to one of your user accounts. So each time I need an email for a site, I just put <site_name>@some_domain.com. This way there's no need for the +alias in the user part, and some site tend to block this because they know it's used for aliases. Doing this, I know exactly where this email was used. Been doing this for years, and works great.