When it comes to creating a backyard wildlife habitat, here are the basics:
Food (including nectar for hummingbirds and butterflies)
Water
Shelter (either natural or in the form of nest boxes) - check here and here for general info, and here for the first in a series of bird house plans if you want to build your own!
It is so much fun to feel the satisfaction of providing for your very own critters! Have fun!