While you can't use Dream World yet, you CAN play an online game to win an Eeveelution who you will meet in Dream World when it opens. Go to www.pokemon.com and sign up for an account, then play the Super Breakout game to win an Eeveelution. The hidden abilities are:
Vaporeon - Hydration
Flareon - Guts
Jolteon - Quick Feet
Espeon - Magic Bounce
Umbreon - Inner Focus (lol)
Glaceon - Ice Body
Leafeon - Chlorophyll
Basically collect as many orbs as you can of the Eevee you want. Be sure to avoid lightning and darkness orbs because Umbreon and Jolteon have terrible abilities (quick feet is a great ability but not on Jolteon.)