The world of online marketing is not limited to just SEO, PPC and Social Media. They are the core elements but there are many things that contribute to the success of those channels that are marketing activities in themselves.
Other online marketing initiatives
You probably have a lot of expertise that is worth sharing. Consider a company blog. Blogging is a great for branding, SEO and social media. Content is the key behind online marketing and blogging gives you a great real estate for creating and sharing original content.
If you are a local business, you absolutely need to be listed in the local indexes available. There is Google+ Local, Bing Maps, TripAdvisor, Yelp and the list goes on. You should make sure you are listed and encourage your customers to give you reviews to increase your exposure.