"R" you protected?
You know that little "R" in the circle you see next to product names and logos? It means that the owner of that mark has registered the name (or slogan, or logo design) with the US Patent and Trademark Office. If you see the "R" next to a name or logo associated with a product/good, it's a registered trademark. If it's next to the name or logo of a non-product-oriented group (like a charity or association) it's a registered service mark.
Businesses have always recognized the importance of "trademarking" their goods, and protecting (fiercely) their brand identity. Nonprofit organizations are often slower to "get that", but the importance of protecting their names, logos, and catchy slogans is no less important. If you run a nonprofit and want to create (or already have) a recognizable identity for your organization via its name or logo, an important step is applying for a service mark registration at the US PTO. Yeah, it's a process (takes a while to wade through it), and there's a fee ($335 last I checked), but if you have a cool logo design, or a catchy slogan that distinguishes you from the rest of the crowded nonprofit field (and you plan to use it for more than a couple years) - get registered!
Can't afford it? Or don't think you'll use a particular slogan or logo design for very long? YES, you can still protect it - even without the formal registration process. Assuming nonprofits generally aren't branding goods, your name, logo design, and slogans are service marks (not trademarks), and you can achieve some level of common law protection from others infringing on these assets by simply putting the little "sm" (with or without the circle) next to the name, logo design, or slogan when you use it on your letterhead, educational materials, website, etc. How easy is that?