The tree shown in the image included with the question is of a Cedar, possibly an Eastern Red Cedar (Juniperus virginiana). The berries are an important food source for birds, and were often historically used by Native Americans for medicinal purposes and as a spice for foods.

http://www.mayacreek.org/pictures/plants...

http://oregonstate.edu/dept/ldplants/ima...

http://pictureplants.com/sites/default/f...

They've always been in my front yard and that's been like 14 years. I've always wondered but never touched. I want to know if they're poisonous or anything.