I think the biggest part of this is making yourself known. Being active and being present to the patrons is highly important. This is especially true with special libraries. I had read an article about a medical library practically being located in the basement of the hospital and many patrons did not even know it existed! Putting yourself out there and actually going to the patron I think is an ideal way to market. I myself am a very personable person and would hope to be face to face to the patrons within whatever organization that I work for. I personally would want to have staff orientations. I am sure with budgets and time it must be hard but currently where I work, patrons do not know the access that they have here at the library. It is not initially discussed during their orientation when it should be! That is one important step in promoting your library is making it known. Plus, those patrons miss out on the benefits of the user services the library has to offer.
A popular way that has taken the library world by storm it seems is Social Media. Libraries have facebook pages, twitter accounts, tumblr pages, blogs you name it. I personally think these are great for academics or public. However, I have my moments of thought when it comes to special libraries. Special libraries are usually much smaller and sometimes ( I stress sometimes) a smaller patron base. I personally feel that newsletters, face-face orientations better serve marketing a special library. It all depends on the type of social media a library wishes to use. Web 2.0 is an ever powering way to market a library, but depending on how you want to use it and what you want to accomplish I feel one should really think if its worth doing. RSS feeds can be a great way to link patrons to articles or newsletters for example.
I am excited about promoting my library someday. It is probably an extremely geeky thing but who wouldn't want to promote something they love to do and what they work hard for. I couldn't imagine taking a backseat and letting patrons miss out on the great user services a library has to offer!