Fidelity InvestmentsFidelity Investments is an American multinational financial services corporation. It is one of the largest mutual fund and financial services groups in the world. It was founded in 1946 and serves North American investors.
In the following it can be seen that Fidelity Investments directs U.S. persons who do not live in America to its international investment site:

Open an AccountThis site is for U.S. residents with a valid U.S. address. Not a U.S. resident? visit our International Investment site.
At its international investment site, it informs U.S. persons that they are denied services at this site.

International Investment siteFidelity does not offer these products or services outside their intended countries or regions, and purchase orders from U.S. investors will not be accepted
As such, Fidelity Investments are available to everyone except for American citizens living abroad, it appears.
So, I called to inquire on the matter. First, I was told that they do not accept foreign addresses. Yet, when I explained that I was an American citizen who does not live in America and that I was denied services at the international site, I was informed that I can open up a US investment account from within the US using my foreign address, or I would have to do so via international snail mail. Sadly, in the year 2012 with all the latest and greatest tech gadgets and possibilities, everyone but American citizens living abroad can open up an account using the internet.