All codes are dead now.

Rip in pepperoni great tutorial.
The alternative now is to use their "get free premium" offer here h(tt)ps://http://www.grammarly.com/referral and invite e-mail accounts; you will get 1 Week Free Premium per e-mail invited and that accepted + registered.
I own 1000+PVA Gmail accounts, so I sent invite to 52 of them, so 52 weeks free premium making it one year. Of course, you have to empty cookies + use a proxy (preferably a VPN, if you have an HMA Acc that makes things easier) for each invite accepted.
Here is the process step-by-step:
1 - Go to /referral and invite 'x' e-mails.
2 - Use a Proxy/VPN to accept the invitation.
3 - You will have to "Add to Chrome" the extension and right after register with a Name / E-mail you invited / Password
4 - That's it now you have a free week premium on your main account.
5 - Clear Cookies, Change IP with your proxy/VPN and repeat from step 2.
I finished processing my 52 invites within an hour. I figured one-year Premium should be enough and by the time it ends a new trick might have come out for us to get this magic tool for free.
