mkpass is a simple command line utility to generate secure random passwords. You can easily redirect these to a clipboard or copy and paste as needed.
I use a password manager and generate random passwords every time I need one. And while most password managers include a generator, there are times I need one outside of that.
The code is written in java so it should run on any OS that supports it. Lastly, the idea and core code came from a Wikipedia article. I just took this and...
An advanced password generator written in C++ and designed to run within the terminalemulator of any *NIX compatible system. It is based on the work by Nintendo(r) European Reasearch and Development (NERD) and the "HireMe" challenge. I've taken the work of NERD a step further and used the input-confusion-diffusion paradigm in conjunction with SHA/256 encryption to generate randomized passwords that cannot be decoded (yet - quantum computers will change this eventually!) ...
The 'jpwgen' program is a Java-based password generator whose functionality resembles the popular 'pwgen' program. The *nix based version of 'pwgen' is available at http://sourceforge.net/projects/pwgen/.