I've decided to be a spectator in some events, since the cost of running all of them is prohibitive on my budget. So far I've been a spectator at The Colorado Marathon and the Lifestyle Centre 5K, and I've taken photos as both. Better than being a spectator, I suppose, is actually volunteering to help with the event, and I'm looking ahead to events I will be able to volunteer at.
As a runner, I rarely notice spectators during a race, but following the example set by a runner at Last year's Turkey Trot (Loveland, Colorado), I've taken to jogging back along the course to encourage other runners as they approach the finish. I'd like to think the other runner's appreciate this, and although many are focused on only the finish line, some wave back and thank the spectators cheering them on. I try to thank spectators and volunteers when I can, too. The events would not be the same, and the sport couldn't grow, if it weren't for them.
So, pick a race you're not running in, or pick a few, and be a spectator or volunteer to help out. Even if you're not sure it doesn't the participants any good, you can feel satisfied that you're efforts are supporting whatever cause the race is raising funds for, and I suspect you'll get a lot of enjoyment out of the experience and you'll probably make some new friends.