I learned to make Sushi out of curiosity, rather than necessity (who doesn't know a great Sushi place?).... The trick seems to be to keep the ingredients simple, fresh and a little bit special.  I recently made a few versions that were particularly delicious:

Blue Swimmer Crab and Black Rice – using sesame mayonnaise.  Black rice is a strange and wonderful thing - it is rice in it's husk, pitch black.  It has an intense nutty flavourn and is also great to add to stir fries as something a bit different. I found a packet at the supermarket and wanted to try it...
BBQ Prawn and Avocado – using spring onions, wasabi and sesame mayonnaise
Salt and Pepper Squid – with pickled ginger and Furikake mix (this is a dry condiment made up of tiny strips of Nori seaweed sheets, toasted black and white sesame seeds)

SushiOf course you can add any filling you like, my other favourites are salmon with dill, chicken with soy, teriyaki beef, cooked tuna...

1 ½  cups Sushi rice
3 cups cold water
3-4 tablespoons Sushi seasoning – which is just half Mirin rice wine and half rice wine vinegar with a teaspoon of sugar
Nori seaweed sheets

You will need a bamboo rolling mat, these are very cheap from Asian grocers, or even at regular supermarkets now.

When rolling your Sushi – keep a little bowl of cold water nearby to wet your hands, it will stop the rice sticking to you and make the rolling easier.

Rinse rice thoroughly before cooking to remove excess starch - wash until the water runs clear -  then place in a large saucepan with 3 cups of cold water, bring to the boil and simmer until just cooked.
Remove the rice from the saucepan and place in a glass/ceramic bowl.  Sprinkle over the Sushi seasoning mixing it in well, then chill for 30 minutes covered with plastic wrap.

To assemble your Sushi:

Place a Nori seaweed sheet on the bamboo mat shiny side down.
Add a generous handful of the rice (about ¼ of a cup) on the seaweed sheet on the end closest to you and flatten, leaving about 3cm of the seaweed sheet uncovered to act as the seam when the Sushi is rolled up.

Place your filling in a layer across the centre of the rice and then gently pick up the end of the bamboo mat closest to you and start rolling away from you.
Keep the rolling as tight as possible, once all the filling is rolled up wet your fingers and dab along the dry edge of the Nori seaweed, then seal the sushi by rolling it forward a couple of times and pressing it down gently.

Refrigerate for a couple of hours, or until completely cold before serving with pickled ginger, soy dipping sauce and toasted sesame seeds. 

For Sesame mayonnaise take 2 tablespoons of very good mayonnaise and add 1 teaspoon toasted sesame seeds, a few drops of sesame oil and a tiny drop of rice wine vinegar.  

A good basic dipping sauce is 2 tablespoons soy sauce, 1/2 tablespoon oyster sauce, a teaspoon of Mirin and a few toasted sesame seeds.