529 plans are organized through each state. Some states offer a tax rebate/refund/credit if you are a resident and contribute to their plan. Here in CT, for instance, we get a tax credit for our contributions (up to $10,000 per year). So, we save roughly 5% of every dollar we contribute to the CT plan.
You can contribute to any state's 529 plan, but you won't get the same tax benefits.
If your state doesn't offer any incentive to contribute to their plan (or you aren't happy with their plan options, etc..) than you should look at Utah's 529. It is handled through Vanguard and is regularly touted as having the lowest fees and most options.
You may also want to look at Coverdell IRAs (also called "Education Savings Accounts"). They have lower maximum contribution limits but similar benefits to a 529 (a few different rules about them, but very similar). In addition to 529s, we have Coverdell IRAs for our kids (through Vanguard).