Mary, two of her friends, and I hiked to the Cascada de Rio Negro (Black River Waterfall). I'd heard about this hike almost since the day I arrived in Trujillo, but never done it. One of the reasons why is that my former sitemate told me he had gotten lost on the way, so I figured the trail was not well-maintained and that I'd have to bushwhack my way through.
That was not the case at all. The hike to the cascada was easy and the trail well-maintained. And the waterfall/swimming holes were beautiful and devoid of people.
There's a pretty accurate description of how to get to la Cascada de Rio Negro in the Lonely Planet Honduras guidebook. There is one inaccuracy: They claim the hike is 1km from the trailhead. Not true. It's at least 2km, probably closer to 3km. But still, it's not a tough hike and is well worth the reward.