Boy, things have come a long way since I first installed SLS Linux on my pc using floppy discs back in 1994
These days I prefer Ubuntu 6.06 LTS server edition. It is supported until 2011 – nice that you don’t have to reinstall the server in a year or two. Furthermore, deprec makes it extremely simple to setup a Rails stack on an Ubuntu server.
nginx. Nginx is fast, stable, lightweight and has easy configuration.
MySQL. It’s the database used by most Rails applications. Furthermore, it has some nice scaling support with master-slave setups. A couple of years ago I used and liked PostgreSQL a lot. I still prefer PostgreSQL’s query analyzer to MySQL’s.