companies? I'm an amature at investing....but are any of these companies worth investing in at all?

USEC - symbol USU
Pacific Ethanol - PEIX
China Biodiesel - CBI.L

For that last one, can I even invest in that company through the American market, or is it reserved to the Chinese market only?

Like I said, I'm an amature =(...Thanks in advance for your answers.
what exactly is a mutual fund? and anyway are the companies I listed 'good' companies to invest in?