3D Video on Youtube.

It's difficult at first, but many people who "freeview" (as it's called) find that cross-eye is the ideal way to view 3D images on screen.

An alternative is to do it Magic Eye-style, looking through the screen so your left eye sees the left image, and the right eye sees the right. This is hard to do with large images: your eyes more easily cross than diverge. To help view it crosseyed, try looking at your finger 4" from your face (you'll go crosseyed), then try to focus on the screen behind it while keeping your eyes trained on your finger.

There are other good things about this way: You get true full color, unlike with red/cyan glasses. Since both eyes are viewing a different set of pixels, the resolution is effectively doubled, so the image appears sharper than normal.