Don't neglect the importance of your group's printed matter in communicating to both members and non-members. Printed matter isn't everything, but it is a visible embodiment of your group identity and as such it creates impressions in people's minds and partly sets the tone for how people will respond to you in the future. Professional looking design can translate into mainstream credibility.

Mailing out a short newsletter 2 or 3 times a year establishes a presence for your group in the lives of everyone willing to give you their address. This list will probably include many people unwilling to take part in actual events but who nevertheless lean towards your point of view. Besides, creating a newsletter is really not all that much work. Mention the accomplishments of your group in the recent past. Thank volunteers (but be consistent). Hype your upcoming events. Crib PETA letter writing alerts. Include photos from the local animal shelter... and et cetera..

For us, having a sign up sheet at every event was essential to our operations. We let people indicate on the sheet whether they wanted to receive information, whether they wanted to be called, and whether they would be interested in volunteering. This way we had a ready pool of people to hit up for support and to mail our newsletter to.