Octave help

Here is the link to Octave's online help document for quick reference.

http://www.gnu.org/software/octave/doc/interpreter/

This link is an Octave Tutorial by Malin Christersson.

http://www.malinc.se/math/octave/thewindowen.php

The Octave Programming Tutorial from WikiBooks which basically taken from the Octave help document.

Octave Programming Tutorial

Since Octave is very similar to MATLAB, here is the link to MATLAB's online documentation.

http://www.mathworks.com/help/techdoc/

Link to an online GNU Octave 3 book by John W. Eaton, David Bateman, Søren Hauberg.

GNU Octave Manual Version 3

http://www.network-theory.co.uk/docs/octave3/

Also check out Octave-Forge. A site that has add-on packages for Octave (they should be in the repository in Ubuntu) with descriptions, mailing list, help, FAQ, etc.

Octave-Forge - Extra packages for GNU Octave