You want to do real-time business with real-time insight, download SQL Server 2014 right now

You can download SQL Server 2014 from the Technet Evaluation Center here:
http://technet.microsoft.com/en-US/evalcenter/dn205290.aspx

You can also download the express version here:
http://msdn.microsoft.com/en-US/evalcenter/dn434042.aspx

You get the following programs in the express edition:

• LocalDB (SqlLocalDB)
• Express(SQLEXPR)--Database Engine only
• Express with Tools(SQLEXPRT)---Install & Configure database server+ SSMS
• SQL Server Management Studio Express(SQLManagementStudio)
• Express with Advanced Services(SQLEXPRADV)--includes Full Text Search & Reporting Services

Summary of some basic requirements:

• .NET 3.5 SP1 is a requirement and is not installed by set up.

Download the above from here:

http://www.microsoft.com/en-us/download/details.aspx?id=22

• .NET 4.0 is also a requirement but the installaiton program downlaods and installs it.
• PowerShell 2.0 is also a prerequisite and you have to install it if it is not present.

Operating Systems on which you can install:

Full list can be accessed here:
http://msdn.microsoft.com/en-us/library/ms143506(v=sql.120).aspx#hwswr

• Enterprise and Business Intelligence versions installs only on Windows Servers (2012 and 2008 R2)
• Standard Edition can be installed on Windows 7(x32 and x64) and windows 7 SP1(Ultimate to Professional)
• SQL Developer covers the widest Windows operating Systems.
• SQL Express can be installed on above mentioned Servers as well Windows 8, Windows 8.1 and windows 7 SP1