PVC Yagi's are a lot like pringles can yagi's. but, using a peice of pvc pipe instead of a pringles can. this is good because it's more weather resistant, more drop proof... and well, it looks less tacky.
http://awip.truffula.net/pictures/8dbi_pvc_yagi_w_shoulder_strap.jpg
here's a picture of my initial test one (with an attached shoulder strap). it gets about 8dBi. i'm somewhat disapointed, but i think was a bit sloppy in the construction. i'm going to make a smaller one using 1" pvc instead of 2", and i'm also going to make a second, and hopefully more precise large one for rooftop mounting at a friends house.
as soon as i start making those 2, i'll post some real directions complete with pictures.