Originally Posted By: Roarmeister
A third option is a bivy bag. About the same weight and volume as a medium sized tarp, it can provide more weather protection.

A fouth option is a Hennesy Hammock.

A fifth option is a tarp-poncho.

Each of these options are single user only whereas a tarp of similar weight can provide shelter for 2 or even 3.

A 6th option is the tipi:
http://kifaru.net/tipis.html

Though you could probably do this with a big enough tarp.