The Verizon iPhone is now available for online orders, both at Apple's site and Verizon's. Pre-orders were available last week to existing customers, some of whom have received their iPhones already, but online orders are now open to everyone.
If you'd rather buy a Verizon iPhone 4 at a brick-and-mortar store, it'll be available on February 10. My guess is there'll be some pretty long lines (and limited quantities) at your local Apple and Verizon stores, so buy online if at all possible and stay warm.
Carrier choice for the iPhone is nothing new in my part of the world, but I'm still pleased it's finally come to my old stomping grounds in the US. If you're just now joining the Cult of iPhone (one of us, one of ussss ...), here's an introduction to the iPhone ecosystem; we also have an iPhone 101 series tailored to beginners.