Commission Free ETFs (make sure to enable them before you purchase any and you must hold them for 30 days before selling). Then purchase VTI (Total US Stock), VEU (basically Total International Stock), and BND (Total US Bond Market) at an allocation that makes sense to you.
iShares has some balanced ETFs (aggressive, moderate, or conservative allocation), but the expense ratios are around 0.37%, which is a lot higher than you could get by just purchasing the 3 Vanguard ETFs.