The US Transportation Security Administration (TSA) officially refers to it as a zip-top bag. I have never heard or read this usage elsewhere, and I imagine it was probably constructed to avoid the genericized trademark Ziploc.
In the southeastern US, a resealable plastic bag is usually called a ziplock bag, regardless of whether it has a zipper or not. This is likely true for elsewhere around the US but I can't vouch for that.
Oddly enough, this Web site features macro-images of the bags and several identifying buzzwords, including slider seal, closures, channel, and double zipper seal.