The Librarities

Go here, read everything, and be sure to look at every picture of of the most meticulously detailed archive of MTG rarities on the internet.  It doesn't stop there.  Go check out the forums where the most knowledgeable collectors in the world congregate and talk misprint.  This is where I started when I first got into misprints.

The Misprints and Rarities Facebook Group:

While the group has become a bit saturated with folks looking to dump their newly opened misprints, this is the current hangout for all of the major and minor collectors!  If you're looking for info, help, advice, or a great place to buy misprints, this is the place to go.  I'm also one of the admins of the group so be sure to say hi!

Squt's Page:

This is a great resource for learning about the layout errors (typos, etc.) that are out there.  It's a bit old and no longer being updated, but it's an invaluable resource!

The Misprint Guy:

There's a good chance that you already know of him, but if you don't I hope that you're ready.  Keith, aka "TheMisprintGuy" has one of the top misprint and rarity collections on the planet.  Oh, and he makes super helpful videos to teach you about all them.

Apathy House:

Has some really useful how to guides and tools that you may find helpful.  They also do this booster of the month club which is a whole bunch of fun!

The Green Disenchant Project:

The site of fellow collector, Neuron, this site exists primarily for his global disenchant collection.  He's a super meticulous collector and he does have some really interesting articles to help folks understand some of the slighter nuances of print variations!

The House of Errors:

It doesn't matter if you can read Japanese or not.  Go here.  Click links randomly (if your google chrome doesn't translate it for you).  See some of the coolest examples of misprint variations out there!  This site is a bit old, but definitely worth a visit.