Feels weird reviving something this long dead, but since it isn't worth starting a new post for....
New WiFi event for Diamond/Pearl/Platinum and Gold/Silver starts today and runs for three weeks.
You can download special versions of the legendary trio of dogs: Raikou, Entei Suicune, which you are then meant to transfer to Black/White (released in March) and they'll enable you to get a new legendary Pokemon.
One beast per week, starting today with Raikou.
Really wish Nintendo would post this news somewhere useful, I only found out after visiting serebii.
Looking For: Wreckers Saga TPB Collection (with Requiem)