According to NOE's website, Nintendo will be giving away a new item
over the wifi. I don't see why this would only pertain to Europe so
get ready. Per the other wifi giveaways all you have to do is
connect to Nintendo Wifi by talking to Booker and saying you want to
go out. Once you see the list of towns you can visit, you can
simply back out and head to your mailbox to check out the goodie.
If its a super rare item, you could get your in-game roommates to go
wifi as well to receive the item again. Your roommate must have a
friend code given to it and have any friend code entered as a friend
(even if the other person has not entered your code). That roommate
will be able to get the letter and item with the previous steps
above.

Source:
http://www.nintendo-europe.com/NOE/en/GB/news/article.do?
elementId=iNjZtu5e8mnVeeluipXuvHy5BwrGrcdI

If you've already picked up Animal Crossing: Wild World, your every
spare moment is probably already spent playing. But we'd just like
to let you know that there's an extra special reason to take a trip
to your virtual town this Easter.

From Good Friday until the end of the Easter weekend, every player
who takes Wild World online, via Nintendo Wi-Fi Connection, will
receive a special letter from Nintendo, delivered straight to their
in-game mailbox, complete with a brilliant free present! Trust us;
you won't want to miss out on this one.

If you're a big fan of the Crossing and you like to get creative, we
have another neat new feature that you might be interested in, too.
Click here to head over to our special Easter E-Card Generator; you
can use one of our pre-designed cards or else design one of your
own, then send it to a friend!

If you'd still like to know more about Wild World, check out the
dedicated Animal Crossing site, here, and our Animal Crossing blog
here. In the latest update, our blogger Luigi has discovered the
dubious pleasure of chopping down his friend's apple tree…

Meanwhile, if you're already enjoying the game but you want to get
the most out of it, we heartily recommend The Official Animal
Crossing Player's Guide, from Future Press (pictured above). With
this full-to-the-brim handbook to Wild World, you can get the
lowdown on special events, read top tips about customising your home
and town, and even check the items catalogue for furniture,
clothing, and accessories.