Roku's little streamer that could, the Roku Streaming Stick, is down to impulse buy territory. The diminutive device is just $35 at several retailers right now, including Amazon, Best Buy, B&H, and Target, among others. That brings it down to the normal price of the base-model Chromecast and makes it a considerably more appealing purchase.
In his review, our own Corbin came away impressed by the Roku Streaming Stick, praising the device's performance. The little dongle matches the form factor of the first-gen Chromecast pretty closely, being a stick (obviously) that hides behind your TV, hanging out of an HDMI input and drawing its power from a USB port. It can't do 4K, but again, it's $35. It's a serviceable and cheap way to bring streaming apps to a dumb TV (or streaming apps that don't suck to a lower-end smart TV).
You don't need a Prime membership to get this price on Amazon, and the listing doesn't say how long the sale will go on. But at this price, why wait?