On occasion, when I am unable to work out on my lunch break, I'll make a pit stop at one of my favorite little places for a quick hike: Arroyo Verde Park. It's a quick 2 mile dirt trail loop around a beautiful park. You get a few ocean views and a good sweat going - especially if you run it.
Afterwards I usually do a few burpees, squats, mountain climbers and pushups on the grass just before the entrance. It's a perfect little workout for those days where you need a little break from the gym life.
Personal goal: To be able to run TWO loops with minimal walking!