I encountered the problem from issue #391 with the latest develop in Ubuntu 12.04 and found it necessary to install ubuntu's packages for all the dependencies on the install page, then make sure to call virtualenv with --system-site-packages so pip did not try to compile those.
https://github.com/saltstack/salt/issues/391
one line added to indicate the need for swig and libssl-dev to be installed. This sort of assumes that those are the correct package names on distros other that ubuntu. Alternatively just indicate generically that 'the libssl development headers' are needed, etc.
