Installed Java SE 1.7.0u10 from Oracle w/ their installer package
Downloaded and unpacked Eclipse Juno (4.2.1)
Double click Eclipse
If you'd like to install Java 6 JDK only (no Java 7 JDK/JRE, no Java 6 JRE only), install the Apple OSX Java DMG (at time of writing, this was http://adcdownload.apple.com/Developer_Tools/java_for_os_x_2013003_developer_package/java_for_os_x_2013003_dp__11m4406.dmg).
You still won't be able to start Eclipse. Make a directory JavaVirtualMachines under /System/Library/Java. And then make an Alias of the java version folder at /Library/Java/JavaVirtualMachines and rename the alias 1.6.0.jdk and copy that alias to /System/Library/Java/JavaVirtualMachines/
After finished, you will have an Alias at /System/Library/Java/JavaVirtualMachines/1.6.0.jdk that points to the Java install directory at */Library/Java/JavaVirtualMachines/1.6.0_XX-XXX-XXX.jdk*