When defining American cuisine, I believe that the peanut butter and jelly sandwich is more American than hamburgers ... or mom's apple pie.
Wiki writes on the standard variations
"Some variants add honey, chocolate or maple syrup, normal chocolate, the hazelnut-chocolate spread Nutella, marshmallows, raisins, bananas, butter, marshmallow fluff, potato chips (UK: crisps), cheese, other dried fruit, or another slice of bread. Other less common variations include slices of fresh fruit besides bananas such as apples or strawberries."
For the most part I prefer it classic ... good sliced white bread with crust, peanut butter and straberry jam. Sometimes I'll toast the bread, but not usually.
I tried it grilled once, like a grilled cheese sandwich, but didn't care for it. The peanut butter was too runny and the whole thing was a greasy mess.
When I was a little kid ... get ready for the eeewww factor ... I would butter the bread, add cream cheese on one slice, peanut butter on the other and then jelly before slapping this together.
My "gourmet" variation ... raisin bread with peanut butter and fig jam.
Funny, yet seriously obsessive link on how to make the perfect peanut butter sandwich
"Avoid using thick bread like Texas Toast. You want to be able to taste the peanut butter and jelly, not get a mouthful of bread everytime you take a bite. The reason you want to use white bread, and not Whole Wheat, Rye or Italian, for example, is that the taste of the bread will interfere with the two most vital ingredients."
"Even if you like crunchy peanut butter, refrain from using it. The best PB&J sandwiches don't make much of a noise when you're eating them; you should only hear the smacking of your lips."
The Food Timeline website talks about the history of the peanut butter and jelly sandwich as well as some peanut butter sandwiches variations
Peanut Butter and Apricot Sandwich
Peanut Butter and Cabbage Sandwich
Peanutpine Sandwich (peanut butter, honey, walnuts, lettuce, pineapple)
Peanut Butter and Prune Sandwich
Peanut Butter and Orange Sandwich (orange juice & peel)
Peanut Buter and Ham Sandwich
Peanut Butter and Tomato Sandwich
Peanut Butter and Pickle Sandwich
Peanut Butter and Ginger Sandwich
Egg and Peanut Butter Sandwich
Peanut Butter & Cherry Sandwich
Peanut Butter and Chili Sandwich (on wheat)
Peanut Butter and Olive Sandwich (with mayo on white or rye)
Peanutraise Sandwich (raisins, peanut butter, brown sugar, salt, lemon juice & orange juice)
How do you like your peanut butter sandwhich?