Do Americans have alternatives to Trump and Clinton that they will be able to vote for in the up coming presidential election?

As in a symbolic non establishment choice? Yes.
As in a viable third option that might actually win? No. Hell, the third choice is polling at about 10% right now.

Someone posted this link on another thread.

Yikes..

http://www.steynonline.com/7216/the-undocumented-branch-of-the-electoral-college/

Most people are aware that the President is elected not by the popular vote but by the votes in the Electoral College. And most people are also aware that the more densely populated states have more electoral votes than smaller states: California has 55 votes, Vermont has three.

But most Americans, I would wager, assume that those proportions are based on the number of citizens in each state. Not so. As Politico reports, each state's share of the Electoral College votes is calculated by using the whole number of persons in each state - including those who shouldn't be there. So the more illegal immigrants you have in your state, the greater the votes you have in the Electoral College. Thus, the armies of the undocumented don't need a pathway to citizenship" in order to change election results - or, as Politico's headline puts it, illegal Immigrants Could Elect Hillary

This math gives strongly Democratic states an unfair edge in the Electoral College. Using citizen-only population statistics, American University scholar Leonard Steinhorn projects California would lose five House seats and therefore five electoral votes. New York and Washington would lose one seat, and thus one electoral vote apiece. These three states, which have voted overwhelming for Democrats over the latest six presidential elections, would lose seven electoral votes altogether.

California&'s illegal immigrants have a greater representation (five votes) in the Electoral College than my entire state (New Hampshire's four votes). Which seems a very perverse system.

So Democrats don't need to nurse illegals through to citizenship; simply moving them into California and other blue states bulks up the Electoral College math in their favor.

I wonder how it would be if they weren't rigged

We will never know as its institutionalized corruption.

yes, primarily people choose to vote democrat or republican though,, so for as long as I can remember,, we always end with one democrat and one republican running against each other

We Americans can vote for anyone we choose. We can even vote for ourselves(write in)or Bozo The Clown(no relation to Hillary).