On Halloween Day, from 6-8PM GMT, SCEE will be hosting a virtual party in the Burn Zombie Burn space. Participants that purchase and wear appropriately undead attire will receive a special "treat" upon arriving. For more details, visit the EU PlayStation.blog.
SCEA is celebrating one day earlier, on Halloween Eve. At 11:59PM EST, the Central Plaza will feature a zombie rally that will put Hamsters vs Humans to shame (cough). Once again, virtual prizes will be handed out to all that participate -- and isn't that so much better than going outside, only to get tooth decay? For more details on America's festivities, visit the US PlayStation.blog.
Source - Halloween comes to PlayStation Home
Source - Celebrate Halloween PlayStation Home-Style at the Zombie Rally