Most of these opportunities come from participation in the chapter and lodge by arrowmen. Some of them are open to all scouts though. A great example of this is the Utah National Parks' Great Western Trail award. There are a number of ways to earn this ward, but all of them involve writing a 150 word report about your experience backpacking and doing service on the trail.
Getting out onto the trail is a good thing, working on a service project approved by the wilderness management agency is even better. Imagine the impact of going out and doing all of that, then coming home and writing about it to cement the ideas, memories, and insights in your mind.
Here are some excerpts from what my scouts wrote in their reports about our experiences on the trail:
Many things made me want to go on the trek. [Another scout] said it was going to be awesome. I also love to camp. And it would just be a good experience to look back on.I'm really glad that the OA put together a program that let my scouts get a better picture of what they can do ... not just in terms of backpacking and camping, but in terms of service and responsibility.
[I had] lots of fun backpacking with the scouts. [I liked] the big meadow where we spent both nights, it was fun. ... [Now I want to do] more, better service projects and more activities to help the community. I want to go on other parts of the Great Western Trail.
[I felt] like my service was appreciated. It makes me want to treat [the trail] with more respect than I have been doing before. ... [When I hike on other trails], I will feel much more grateful for those men, women, and children that gave up their time to make it look better and keep it clean.
I remember [our service] was hard work but the payoff was great, it was good to help the trail. It improved my outlook on [service] because of the satisfaction of doing it.
I remember cutting off all the branches on the trail hanging over and how fun it was to cut down a really big one. Ranger Polly taught us ... what to cut down and how to be safe with the [tools].
It made me see that just doing service does not mean it has to be boring, it can be really fun and cool. It made me feel good that someone ... noticed what we did.