Where to get the tools.jar to use with the Java 8 jdk early release

You just need to install devel package. On RHEL family it's like this:

# yum install java-1.8.0-openjdk-devel

The tools.jar file on the 1.8.0 JDK is located in jdk1.8.0/lib/tools.jar. If it's not there, then you don't have the JDK installed correctly.

Please see the accepted answer - the tools.jar file was omitted in a specific early access revision (jdk-8-ea-bin-b106-windows-i586-05_sep_2013.exe).