Sony has announced that, as part of the "Welcome Back Program" for PSN network users, Killzone and CoD's PS3 players will receive double XP and that Killzone: Liberation (a portable game) will be available as download for free.

The promotion has already started and will end on May 23 for Killzone and May 24 for Black Ops (10:00 AM Uk time, 5:00 AM East US time). It was also announced they would add a Nuketown 24/7 playlist on Black Ops, claiming this map has a high kill count and would be a great combination for this weekend.

Here's a link about Nuketown's "secrets": http://oneofswords.com/2010/11/9-cool-things-about-nuketown-in-black-ops/

Read more at:
http://blog.us.playstation.com/2011/05/20/welcome-back-to-killzone-3-with-a-double-xp-weekend/
http://blog.us.playstation.com/2011/05/19/enjoy-double-xp-for-call-of-duty-black-ops-this-weekend-%E2%80%93-only-on-ps3/