It is a common misconception that Sushi means Raw Fish. Sushi is actually vinegared rice, which is then topped or rolled with a variety of things -- sometimes raw fish, sometimes cooked seafood, and to the delight of megatarians everywhere, sometimes veggies! Dining out, sushi can be relatively costly, depending on how many pieces you want and containing what. At home it's much less expensive, and you can put whatever you want into it without confusing the waitress or being charged extra for "special" orders or avocado.
There isn't a recipe for sushi as much as there is a method. Ergo, I've photographed the method.
You will need:
Sushi rice (short grain white "sticky" rice - often labeled "SUSHI RICE." Glutenous rice also works well, though the people at the Asian market have given me a stern warning about it NOT being sushi rice)
Rice wine vinegar
Nori (sheets of seaweed, available at your friendly neighborhood Asian market)
Things to put in your sushi (veggies, tofu, seitan, whatever you like)
Soy sauce for dipping
Pickled ginger/Wasabi (optional)
Highly recommended: Sushi rolling mat. It only costs about $1 at said Asian market. If you don't have one, a piece of waxed paper will work in a pinch.
Prepare the rice according to package directions. I typically use 2 cups of rice and then the appropriate proportion of water and that makes about 6 rolls.
Once the rice is cooked and cooled a bit, season it with vinegar, sugar, and salt. For 2 cups of rice I use 1/4 cup rice wine vinegar, 1 tbsp sugar, 1 tsp salt. Adjust according to how much rice you're using and to taste. Fold the rice over a few times after you've added the seasonings to distribute it evenly.
On your rolling mat, place one sheet of Nori. Add a scoop (about 1/2 cup) of rice and spread it evenly over the Nori using your fingertips, lightly moistened (keeping a bowl of water around doesn't hurt during this process!)
On the side closest to you, layer whatever fillings you are going to use. Here I've got sauteed shiitake mushrooms, avocado, cucumber, carrots, and red peppers.
Start rolling the sushi away from you, using the mat to help guide the roll and hold it together. When it's all rolled up, give it a gently squeeze in the rolling mat to seal the edges. Don't squeeze too hard or your veggies will go flying out the end!
Now all that's left is slicing it into bite sized pieces. I find a wet, serrated knife works best for this. I slice my rolls into 6 or 8 pieces, depending on how fat the roll is. You're supposed to put the entire piece in your mouth at once, so let that be the judge of how big you want the pieces!