Video marketing - make a video talking about a typical problem your niche faces and post it on youtube. Choose the key words carefully. Make sure your phone # is in the video title.
Forum marketing - find forums which your target market is gathering on. Answer their questions. Develop a reputation. Have a signature or profile page that leads them to talking wtih you.
Linkedin/Facebook marketing - Get into groups your target market is in. Engage with them. Develop your rep as the expert.
Each of these costs your time, but you can generate leads and sales with them.