I think you're asking how to contribute to conservation efforts without spending a lot (which is a concern for me too) so here goes...
If you want to participate in conservation for as little money as possible, I'd suggest writing your representative in Congress to support responsible wildlife management. You're paying taxes anyway, might as well get your money's worth by speaking up. Now you can even go to change.gov and tell the incoming administration what's important to you as a voter - so you can write the future president and tell him to support conservation efforts!
Museums (at least the Natural History Museum in NC) accept volunteers to help with educating the public about the environment and conservation. You can do this on your spare time and learn a lot and it won't cost you a cent.
Also, not-for-profit conservation groups like the WWF and UNEP can give you info about what you can do for free. UNEP even offers internships if you would be interested in working in conservation. Note: non-profits do ask for money. It's true. But they're grateful for time as well as for money, so it never hurts to ask if an org wants volunteers.