Did you hear that HTC just announced its new One phone? It looks pretty cool. Naturally, at least some people will be clamoring to get their hands all over this. Those people can kindly be directed here, where the Taiwanese manufacturer is accepting email sign ups for people who want to trade in their old handsets.
The language is actually mildly antagonistic towards competitors ("Upgrade to HTC", "Everything your phone isn't"...maybe the company is ready to get more aggressive with its marketing?), but the message is clear: if you have an old phone, you get at least $100 towards the purchase of a new One. While it's possible you can get more—the page promises "either $100 or the trade-in value of your old phone-whichever's greater"—chances are most devices that you're willing to part with will not get you much more than the baseline.
Still, it's better than letting that old Captivate collect dust in your drawer. You said you'd put it online months ago, but you still haven't gotten around to it. Maybe it's just time to move on?