Patterns, writing letters and numbers, identifying more complex shapes, in addition to the fine and gross motor work that is an extension of his twice-weekly occupational therapy.
We really like Letter of the Week and it worked well for our first, but he was not really thrilled by it so I've been making it myself and just running with whatever he's interested in at the moment.
Nothing formal, really. Daily we do a letter, a number, a shape, therapy work, and he listens in and takes part in my first-grader's history, health, and science.
I print off his work daily and have a 3-inch three-ring-binder where I keep his finished work. We don't grade. He does his work and I work with him to make sure it's done 'right,' but it's really just teaching and guiding him through concepts, not something to be graded.
It's never too early to start phonics. We just start with each letter and what sound it makes. The LeapFrog refrigerator magnets with the ABC's has been an awesome starting point for all my kids as toddlers. They just play with it while I make dinner every night.
Also, read, read, read! Never underestimate how much they learn purely by being read to.