For all those fans of Rilakkuma you will be pleased to hear they are opening a store at Tokyo Station on the 20th of February. Here is a snapshot of the web advertisement for the store from the San-x website. You can get full details here at the San-x Rilakkuma site.
The store is locate in Ichiban-gai (First Avenue) of the Station underground mall on level B1. Here is the link for the official site of 東京駅一番街(First Avenue at Tokyo Station). The site appears to be in Japanese only.
Updated April 23, 2009 I made a visit to this store recently and posted some pictures here.