As noted recently, OS X comes with OpenSSL 0.9.8 by default, which is too old to build Tor.
During the Tor patch workshop today, rl1987 and Yawning were testing the OpenSSL and Tor builds on OS X.
I've put the OS X build steps they used on the Tor Wiki, along with the alternative method of obtaining OpenSSL and/or Tor via MacPorts:
https://trac.torproject.org/projects/tor/wiki/doc/MacBuild
If you're building Tor on OS X, please try these instructions, fix any mistakes, and add missing steps or other alternatives. In particular, HomeBrew instructions for OpenSSL and Tor would be really helpful for some users.
teor
teor2345 at gmail dot com pgp 0xABFED1AC https://gist.github.com/teor2345/d033b8ce0a99adbc89c5
teor at blah dot im OTR D5BE4EC2 255D7585 F3874930 DB130265 7C9EBBC7