Troma Films, the wonderfully trashy home of The Toxic Avenger and Class of Nuke 'Em High has a special treat for shlock fans. They have uploaded around 150 of their full-length films to YouTube. That's right, you can watch flicks like Rabid Grannies, Space Zombie Bingo! and Zombieggedon in their entirety, for free, and it is entirely legal.
Some titles that I particularly enjoyed:
Poultrygeist: Night of the Chicken Dead
Why spend Labor Day outside, barbecuing with your friends when you could hole up inside and watch garbage?
For the complete selection of flicks, visit Troma's YouTube page