Just roll up what ever you want in there. Be sure to use the right rice though, the best for sushi is short grained rice because it is stickiest when cooked. Its hard to actually find a bag of rice labeled "short grain", but it is the same thing as the stuff called sushi rice.
I like temaki sushi the best because it is easier to roll. Just take a nori sheet and cut it in half to crate a long rectangle, and put about a spoon sized ball of rice on one corner. Then pile on what ever ingredients you want on top of that and roll it into a cone and enjoy!
Some of my favorite ingredients are:
crab
celery (cut long and thin)
carrots (long and thin)
sprouts
avocado
lettuce*
spinach
mushrooms
scrambled egg
sesame seeds
wasabi paste
spirachi sauce (red chile sauce, bottle has a picture of a rooster on it)
*You can actually substitute lettuce for the nori in temaki sushi. It makes it a little more easy for people with plate fright to eat because you can get away with not calling it sushi. And lettuce will be easier to find in little mom and pop grocery stores way out in the middle of nowhere too.
If you're looking for raw fish recipes, I believe that is called sashimi but I may be wrong. With those you pretty much just get the absolute freshest fish you can find and cut a small thin chunk and put it in top of a ball of rice, held in place with a dab of wasabi paste. Salmon and tuna are my favorite, octopus is good too but a little chewy and rubbery for my liking. But be absolutely sure it comes from a good market and is super fresh and never frozen! If it has any odor or slime to it, don't use it raw! :snorkel: