With investment returns and withdrawals free from federal taxes, and additional tax breaks in many states, 529 plans are your best choice (so long as you sidestep pricey broker-sold ones).
Check to see if your state offers a tax break by visiting savingforcollege.com. If it doesn't, there's no penalty for using another state's plan.
Go with an age-based portfolio that dials down risk as your child approaches college age.