Microsoft has released Service Pack 1 for Exchange 2013!!
This may not seem like a big deal but the past has shown that a large number of organizations have waited with baited breath for the release of SP1 before upgrading their Exchange On-Prem installations. If you are one of those companies this is your time to shine, as there are tons of great reference material for Exchange 2013.
I thought it might help to list out a few sites/resources to get you started on building up your Exchange 2013 knowledge. There are literally thousands of sites out there, so if you have one you'd like to share feel free to add it in the comments.
This list is in no way meant to be the be all end all list, I'm just trying to give you a few good places to start you journey that hopefully culminates in a brand spanking new Exchange 2013 Installation.
First off take a look at the announcement of Exchange 2013 at the Exchange Team Blog: http://blogs.technet.com/b/exchange/archive/2014/02/25/exchange-server-2013-service-pack-1-available.aspx
Remember that SP1 is a full build of Exchange so go download it here and get started in your Lab: http://www.microsoft.com/en-us/download/details.aspx?id=41994
For a primer on the Exchange Architecture changes in 2013 from the team that built it:http://blogs.technet.com/b/exchange/archive/2013/01/23/exchange-2013-server-role-architecture.aspx
Go to the source for Exchange 2013 info at TechNet:http://technet.microsoft.com/en-us/library/bb124558(v=exchg.150).aspx
Start here on TechNet for learning how to plan out your upgrade from 2010 or 2007 to 2013:
http://technet.microsoft.com/en-us/library/jj898583(v=exchg.150).aspx (2010)
http://technet.microsoft.com/en-us/library/jj898581(v=exchg.150).aspx (2007)
Get the Exchange 2013 Server Role Requirements Calculator:http://gallery.technet.microsoft.com/Exchange-2013-Server-Role-f8a61780
Paul Cunningham at Exchange Server Pro is a great resource to check for all things Exchange, he's an amazing engineer who has a passion for sharing. Check out his site on a regular basis but make sure to see his Exchange 2013 pages in particular:
http://exchangeserverpro.com/exchange-server-2013/
The venerable MSExchange.Org site is still a great resource for all things Exchange. This should get you started on getting your arms around Exchange 2013.
As always we at Anexinet would be happy to help you in any capacity to ensure that your Exchange upgrade project is delivered on time and on budget!