Make it Easy to Unsubscribe from your Email List

You missed another big one: If you're based in the US, it's the law.

The CAN-SPAM Act has many faults, but it's actually surprisingly explicit about unsubscribe process. If people have to click through multiple pages or supply any information beyond email address, you are probably in violation and could be fined by the FTC.

I'm surprised Gmail doesn't have this type of functionality. It could try to keep track of what email lists it thinks you are subscribed to, and then let you manage them all from a single page (with links to external sites if Google can't remotely manage it).

Seems like a pretty straight forward feature addition.

It's not going to solve the problem of an email list that is almost impossible to unsubscribe from, but it would still be cool to just see all the email lists that you're subscribed to in a single place.