Here's my experience installing OpenERP Server v6.1 on a Mac OS X 10.8.2, I'm pretty sure most steps will be quite similar.

You'll need to have MacPorts installed first www.macports.org/index.php (in a simple way, it's kind of apt-get replacement for Mac, correct me if I'm wrong about this)

Unfortunately it requires Xcode (you will need to download Xcode from the Apple developer website, register for free user first). Be aware that Xcode itself is quite big, I downloaded xcode4520418508a.dmg it was 1.7GB in size. Here's a good place to continue the Xcode & Macport installation process. guide.macports.org/chunked/installing.xcode.html

Next step: PostgreSQL 9.1 Download here: www.enterprisedb.com/products-services-training/pgdownload#osx

I had mine installed in:

/Library/PostgreSQL/9.1

Open 'Terminal' and type:

sudo -i
export PGHOME=/Library/PostgreSQL/9.1
echo 'export PATH=/Library/PostgreSQL/9.1/bin:$PATH' >> $PGHOME/.profile
exit

Next step: Create user account that OpenERP will use to connect to PostgreSQL (you can follow the same step in Linux installation guide)

Next: Install all OpenERP Python dependencies:

sudo -i
port install python27
port select python python27
port install py27-setuptools; easy_install setuptools
port install py27-psycopg2 +postgresql91; easy_install psycopg2
port install py27-reportlab; easy_install reportlab
port install py27-lxml; easy_install lxml
port install py27-tz; easy_install pytz
port install py27-yaml; easy_install PyYaml
port install py27-mako; easy_install mako
port install py27-dateutil; easy_install DateUtils
port install graphviz +python27 +no_x11
port install py27-parsing; easy_install pyparsing
port install py27-pil; easy_install pil

You may try download OpenERP 6.1 source, run and test if there are still dependencies unmet. Try to find the unmet dependencies package name and install it by running this command:

sudo port install <package_name>

All the other steps would be quite similar to Linux.