Bernie Heer in his Contractor Profit Zone blog advocates for client appreciation events, where you invite recent and potential clients, and key referral leaders, for an in person than-you event. I agree with him that this sort of activity will generally be a much more effective marketing idea than conventional advertising because, done right, you should earn well more than the cost with valuable leads and referrals (and some worthy repeat business).
He suggests an idea to induce attendance and make the event more fun:
With your invitations, send a sealed envelope and mark it “No Peeking.”
You must explain that this envelope holds a certificate for a prize and the individual will get the prize only if they attend the event and do not open the envelope prior to coming.
Most envelopes will be small value gift cards for a local coffee shop or restaurant, movie tickets, etc. But a small number of envelopes will hold great prizes, like an iPod, Kindle Reader, or similar prize. You can even give away a single big prize like a 50-inch TV if that is in your budget.
Imagine the fun atmosphere as you go around the room and each person opens their envelope.
Nice idea — and for higher-end projects, the cost-per-lead will be well within your budget.