You could write books on SQL Server reference and study material.  Here are some of the ones I use.

BOL

Still and always one of the best places to find out things about SQL Server.

• 2000    Believe it or not I still have to look up things from SQL 2000
• 2005
• 2008
• 2008 R2
• 2012
• 2014

 

MCM Videos

Probably some of the best free training out there.  You can also check out their MCM Pre-Reading List.  Be forward this stuff is somewhat advanced.  Make sure you are at least somewhat familiar with the subject first or you could be watching the video over and over again before you gain much understanding.  And some other web casts by SQL Skills.

 
SQL Bits

More free training videos! SQLBits provides access to video’s of their past sessions.

 
Practice Tests

I like practice tests.  Probably one of my favorite study aids.  I do the test, and then study whatever I got wrong.  Not just the answer to the question, but the whole subject.

• Transcender
• MeasureUp

 

Books

• Huge list of Microsoft books including almost 30 SQL Server books available to download in several formats.
• More Free Books!
• RedGate Books – Some of these have free PDF downloads available.

 

Forums

These can be a good place to read up on what kinds of problems other people had.

• SqlServerCentral
• SqlServerPedia
• Microsoft’s Forum
• DBA.StackExchange.com

 

Blogs

On the same vein as forums.  There are hundreds out there.  Here are a few I follow.

• Midnight DBAs
  Jen and Sean McCown have a fairly good sized library of training video’s aside from their excellent blog. This is where I got started with PoSh.
  They also have a fun web show they do almost every Friday night.
• Brent Ozar
  • Their Blog
  • Their Video Archive
  • Make a point of registering for their Triage Tuesdays here.
• SQL Authority
• SQL Skills
• SQL Rockstar
• Adam Machanic
• VoiceoftheDBA
• ScaryDBA
• SQLPathy
• The SQL Pro
  This one is new to me but I’m enjoying it! Check out the SQL Pros new SQL Snacks!

 

Other

• Pass TV is a youtube channel with recordings of a number of sessions from old Summits and 24 hours of pass.
• Microsoft Learning
  • Of course Microsoft has a learning page for all it’s products.  When I’m studying for a certification I find it’s very important to look at the skills tested for that exam.
  • Microsoft also has the Microsoft Virtual Academy. This site has a number of different “courses” that include some very good free video’s on a variety of subjects.
  • Microsofts virtual labs. Not just SQL Server and they are quite good.
• DBAReactions
  • Not really study material but everyone needs a break.
• SSWUG
  • Lots of great training available.  They even have some of my blog entries featured so you know their stuff is quality.
• Zilckh’s page on Microsoft’s virtual labs
  • Zilckh lists a number of links for Microsoft virtual labs. I haven’t tried one yet but they look very useful!
• SqlServerCentral’s Stairways
  • These are kind of a mini book made up of articles posted by one or two people.