There is a "report spam" button in mine (perhaps enabled via the Labs?), which, when pressed, will stick it in the spam folder and subsequent messages that look like it too. Additionally, if the email actually contains what looks like a valid "unsubscribe" button (required by law for businesses spamming from the UK, I believe), it will ask you if you want it to try and use that link.
As an alternative, buy your own domain and have one personal account that only gets sent to friends/contacts and very trusted parties, and then invent an email address for *every* service you subscribe to (with my service, I can define a set number of email accounts, but additionally have a rule for "all mail received on this domain gets delivered to this email account", and I think in the service I can specify some filters to discard received emails to a specific account).
For example, I'll have a personal account of siasl@mydmain.com, but if I sign up to a service, I will just use a new email servicename@mydomain.com, and my auto-forward from my email provider will give me any emails received. Later on, if I start getting adverts for various pills and other such junk with a target email of "servicename", I can specify a filter to discard all of those and, as an added bonus if I could be bothered, I can pursue that service in small claims court for up to £300 as I will have evidence that they've distributed my email without my permission (as I never tick/untick the box about "trusted partners").
True, a little cash is required annually to support this, and you need a bit of technical know-how - but it's not rocket science.