I use regular lawn sprinklers and make custom-length garden hoses. I "permanently" place the sprinklers and hoses in areas that are out of sight and set them on timers. Once the system is in place a set on the timer, I can leave it and forget about it. The system is completely modular and can grow with your needs. The best part is, if you ever move, you can take it all with you and use it at your next place.
Step 1: Plan
How much of your yard do you want to water?
Where can you put a sprinkler to reach the maximum amount of area, yet remain out of sight?
Where are your outdoor faucets located, and if needed, can you add another one? (that's an instructable for another day)
Where will hoses need to be run, and can they be hidden in flower beds, under a deck, etc.?
Browse your Home Depot or Lowe's to figure out what sprinklers will best fit your needs. Sketch out your yard. Get creative! This is the most fun part.