Their new deal booking page takes a little navigating, but there are flights leaving from Boston, Los Angeles, Miami, New York, Pittsburgh, San Francisco, and Washington D.C. carrying departure dates from March through October.
The deals are taking you to one of four locations (and the easiest way to dig up prices is to follow one of these links to the deal page for that destination city). You can head to Berlin, Germany; Copenhagen, Denmark; Frankfurt, Germany; and Stockholm, Sweden.
It's worth noting the airline you'd be flying with at this point. You'd be flying with WOW Air, which is a budget airline. Often, the tickets are cheap, but if you bring more than a backpack you get nicked for luggage fees (this can include a carry-on fee). So, this can be a cheap trip, but it's worth looking into the fees before you book and are surprised to find out that the flight isn't nearly as cheap as you were anticipating. However, if you can pack super light, they're a good option to get to Europe on a budget.