It happened yesterday, August 27th, on the north flank of Pu’u O’o crater, in Kilauea’s East Rift zone. (Sorry about the ads, but these guys do deserve something for getting such incredible footage.)
Here’s a link to the Hawaiian Volcano Observatory’s Kilauea page. To see the new lava field, choose webcams and then Pu’u O’o North Flank. I think the silver stuff I saw in the distance through that cam just now is lava. In their update, HVO says none of these flows is an immediate threat to people.