Need JDK6, but JDK7 won't go away!
Whatever development environment you're using, you can probably explicitly set it to use JDK 6, by setting $JAVA_HOME or changing preferences in an IDE like tor commented. But if that doesn't work for you, here's how to get JDK 6 back as the system default.

The Apple JDK 6 is installed on your machine; it's just being masked by the newer JDK 7. OS X's Java indirection layer will prefer newer versions. You can verify that it's there by doing /usr/libexec/java_home -v 1.6.

The Oracle JDKs live in /Library/Frameworks. You can remove them by just deleting them.

sudo rm -rf /Library/Java/JavaVirtualMachines/*.jdk
sudo rm -rf /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin
sudo rm -rf /Library/PreferencePanes/JavaControlPanel.prefpane


You're out of luck on the Java Preferences. Apple removed it in an update. But when you eventually install a newer Oracle JDK again, you'll get a Java control panel with similar functionality.