Bukkit

1. Get Pinapp at http://dev.bukkit.org/server-mods/pinapp/

2. Set it up the usual way, especially let it do its first-run setup.

3. Open Pinapps configfile at plugins/Pinapp/config.yml

4. It should look like this:

worlds:
    world:
        id: 14
        seed: 2011030327
        generator: Default
        env: Normal

5. Now add a new entry for the world you wish to use Nordic with:

worlds:
    world:
        id: 14
        seed: 2011030327
        generator: Default
        env: Normal
    my_epic_nordic_world:
        id: 89
        seed: ileikturtes
        generator: Nordic
        env: Normal

if set up like this, pinapp will create a new world named my_epic_nordic_world with the seed ileikturles. The id is the Block-ID you wish to use create a portal to the world the id belongs to. So in this case a glowstone portal would port you the nordic world.

make sure that there are only spaces and no tabulators in the config.yml, as the bukkit .yml parser really doesn't like tabulators. save the config, do a /reload or restart the server and you should be able to go to your Nordic world with a glowstone portal