Running is good for cardiovascular health but avoid doing it to much. Traditional running uses up muscle and if overdone has the potential to actually make you age faster. Plus with your body type being on the leaner side you can easily make yourself to skinny.
I would personally recommend doing anything that encourages you to sprint. Me personally I like going to my local rink or skate park and do this thing where I skate fast on straightaways and slow down on turns.
Anyway the technical name for it is high intensity interval training (HIIT) and the benefits are great. Not only do you get your workout done faster (9-20 minutes) but you can even build muscle. You can also use anything to do it (treadmills, ice rinks, stationary bikes, basketball gyms, football fields, eliptical, etc).
The benefits are summed up best by this picture. On the left is a long distance runner on the right is a sprinter.
Also I would encourage you to invest in a set of kettlebells as kettlebells help you engage in both strength and cardio training. Here's some more links on HIIT.
HIIT: Supercharge your Fitness and Fat Loss
High-intensity interval training - Wikipedia, the free encyclopedia
Also one more picture for the road.
