Oracle Java 7
Oracle has recently declared Java 7 to be fit for general use.

Currently there are no .deb packages available for Oracle Java 7. The raw binaries (without installer) can be downloaded directly from Oracle (Oracle Java download page).

Installing Oracle Java 7 by a script or from the command line

You can install the newest and secure Oracle (Sun) Java 7 by a script (JRE only) or by a command line method. Both are easy to apply.

Script (JRE only)

Only supports Oracle (Sun) Java 7 JRE (which covers the needs of 99 % of all computer users). It pulls the packages from Oracle's website and installs them, comparable to the way Adobe Flash Player is being installed. Plus it adds a dedicated repository, from which you'll receive updates automatically.

http://www.duinsoft.nl/packages.php?t=en

Command line methods

Do-it-yourself methods, but very easy to apply (basically: you copy/paste some terminal commands).

How do I install Oracle JRE 7?

http://sites.google.com/site/easylinuxtipsproject/java (for JRE, more extensive explanation of the commands than in askubuntu.com)

How do I install Oracle JDK 7?

How do I install Java?

There is also an RFE opened on Oracle bugtracker to provide the debian package/installer for Java 7. Please consider voting for this RFE.