There’s more to the health of a Stack Exchange site than having a lot of questions and answers. A site absolutely needs on-going, sustained voting to build a class of leaders that help run and govern the site. Without leadership, there can be no community. The progress of this site depends heavily on having enough users with sufficient reputation to properly lead and govern this site.
How can we encourage people to vote?
First!, if you haven't used up all 30-40 of your votes today, stop reading now and go cast your votes. Find a few dozen questions and answers with less votes than they deserve and go vote for them. When all your votes are all gone, come back and we'll talk. Go now! <grin>
Welcome back. The answer is actually deceptively simple. You have 30-40 votes per day — are you using them? I know that "be the change" sounds a bit trite, but I see a lot of great posts with zero or one vote. So zero votes becomes one; one vote becomes two; everyone reading this post has the ability to SINGLE-HANDEDLY increase the total number of votes on many great posts 50-100%…!
So go do it.
Seriously, when a user finds your site through search, if the post has little to no voting activity, it starts to look like a throw-away feature — "why bother?" — but, if the voting looks like an integral part of the post itself — 2, 10, 50, 100+ votes — suddenly voting looks like the thing to do on this site, and people want to join in on the fray.
Users will generally imitate what they see
The best way to encourage wide-spread voting on a site is to vote yourself! If you haven't run out of votes yet today, don't think in terms of how to get other people to vote; go do it yourself. Before you know it, it will simply become a part of the fabric of the site.
Vote early, vote often