On a clean install.... run  install_packages.sh and everything should work.

At the moment a few tests fail,  but I *think* this is expected.

This gets you to the end of rake test on the Wiki Page:
http://wiki.openstreetmap.org/wiki/The_Rails_Port#Running_the_tests

If all is well then:
ruby script/server

Should start the webserver and you should have access to this at:
http://localhost:3000/

Note at the moment, this just uses a default database password of openstreetmap, If you
want to change this then run:

sudo su postgres
psql -c "ALTER ROLE openstreetmap WITH PASSWORD 'yourpassword'"

Also change the password in config/databases.yml