Here's a very nice deal that will appeal to you if you like Spotify and have pondered buying a Chromecast. If you purchase a three-month Spotify Premium subscription, you'll receive a Chromecast dongle entirely for free. The subscription itself costs $29.97.
The offer is only valid in the US and the UK, and it expires on February 28 at 11:59 pm CET. There's also a limit of one Chromecast per person. One important caveat here is that you can't take advantage of this deal if you are a current or previous Premium subscriber, even if you've just used a free trial of the Premium functionality in the past.
You need to sign up for Spotify Premium using this link if you're in the US or this link if you're in the UK. Then, within a week of that, you'll receive a voucher for the Chromecast in your email inbox. The voucher can only be used at the Google Store.