I change the oil every 2500-3000. As long as you're using a quality filter and checking the level and quality of your oil every other drive, you'll probably be ok. Generally speaking, the harder you drive your car, the more often you'll need to change the oil.
Fuel filter is recommended every 15k miles or so. This is critical in maintaining a free flowing fuel system and prevents fuel starvation which can lead to a blown engine.
Check your tire pressure once a week or so, adjust accordingly (remember, tires are porous and lose pressure over time).
Check your brake fluid every 3-4 drives to make sure that the screen is clean and you've got enough.
New plugs every 15-30k isn't a bad idea. Problem is that replacing them is a pain, so don't go crazy here.
Wash the car every couple weeks if not more frequently just to make sure you're keeping it nice and happy
Oh yeah, and inspect your tires every couple weeks to make sure that your tread is still in good shape and that you're not getting screwy wear on them. If you have all the same tires all the way around, rotate them every 5k to help even out the wear.