Better Choice Online via Amazon offers the Dell U2917W UltraSharp 29" 21:9 Ultrawide IPS LED-Backlit LCD Monitor, model no. HKCH2, for $349.99 with free shipping. That's $30 under our mention from two weeks ago (although that came bundled with a $150 Dell gift card) and the lowest outright price we've seen. (It's the best deal today by $38, excluding the below mentions.) It features a 2560x1080 native resolution, 5-port USB 3.0 hub, DisplayPort, mini Displayport, HDMI, and height-, tilt-, and swivel-adjustable stand.
A couple of close prices: Jet.com has it for $352.98 with free shipping, and Dell Home has it for $356.24 with free shipping via its Member Purchase Program.