Have you thought about sharing tips/suggestions for the next 15 days about tax season? Then after tax season, what people can do who forgot to file? This is your time of year - and the rest of the world is also thinking about it! Find some tax related infographics online & repurpose them by writing content about taxes, answer tax questions for "free" on your business facebook, and write some blogs & then distribute them through sites like Stumble Upon (and other link submission sites).
Hope that helps a little bit. Our Long Island Marketing Firm
does marketing for accountants & definitely like to do more during the tax season.
I'd also recommend using LinkedIn, as it's a great business related social business site and you can connect to others in your industry.
Let me know any other questions you might have and I'd be glad to help (if I can