Quick update: Oracle has released a Critical Patch Update for Java 6 (JDK 6u41) and 7 (JDK 7u15). Also, 6u41 is the last public Java 6 release and Oracle no longer recommends using it in production, so if you're using it, you should upgrade to Java 7.
For more information, see the release notes:
The latest Oracle Java 7 (7u15) and 6 (6u41) are already available in the WebUpd8 Java PPA so Ubuntu users can easily upgrade to the latest version.
With these updates, I've created a new package for all Java versions which provides the Java environment variables (JAVA_HOME, PATH, etc.) and sets that Java version as default. Instructions on how to install this package are available in our updated Java posts (instructions in the links below).
For how to install Oracle Java 6, 7 or 8 in Ubuntu / Linux Mint / Debian, see the following articles: