As you are looking for ways to develop your firm's brand, you might consider offering to speak at events that are not directly tied to your target market. Recognizing that you have limited time and resources, most of your efforts should be spent demonstrating your expertise to the market segment that is appropriate for your firm. However, now and then, it is a good idea to give back to the community, speaking at career fairs, entrepreneurs' conferences, and other training programs where your experience adds value but the audience may not be a perfect fit for the firm.
Doing good feels good. Helping out others in the business community without any self serving motive also feels good. While you may not have much time for this sort of volunteering, it is something you should do occasionally. Whether you are conducting a training clas on "How to Read a Financial Statement for Start-Ups" or you are helping a new business owner with a cash flow projection, giving your time and sharing your insights can be a rewarding experience.
Smaller firms don't have the budget for major ad campaigns or direct mail programs- but when you are recognized as a leader in the community and your firm has a reputation of helping others, it can be as powerful(or maybe even more powerful) than any paid branding initiative!