There seems to be a lot of great stuff on Xbox LIVE Arcade and Marketplace this week, as told by Major Nelson.

New games available now on LIVE Arcade show up in the form of the hotly anticipated Penny Arcade Adventures On the Rain-Slick Precipice of Darkness, Episode Two, featuring the adventures of web comic duo, Gabe and Tycho, as they uncover further mysteries. There’s also the quiz game, Are You Smarter Than a 5th Grader; “Do you think you are smarter than a 5th grader? Now is your chance to prove it! Over 6,000 questions in 21 subjects that test your mental mettle.” Each game is yours for the princely sum of 1200 Microsoft Points

In addition, there new game demos to keep your attention, including Rare’s Banjo Kazooie: Nuts and Bolts and the aforementioned Tomb Raider: Underworld. Even more downloadable content is available for your perusal with a free Marble it Up! Multiplayer level and an extra Achievement. The last bit of DLC for now is the new set of Rock Band songs, now on Xbox LIVE Marketplace. The full list follows below:

• Siouxsie and the Banshees Track PackPack 01 (440 MS Points)

  • Hong Kong Garden
  • Kiss Them for Me
  • The Killing Jar

• The Killing Jar - Siouxsie and the Banshees (160 MS Points)

• Kiss Them For Me - Siouxsie and the Banshees (160 MS Points)
• Hong Kong Garden - Siouxsie and the Banshees (160 MS Points)
• Well Thought Out Twinkle - Silversun Pickups (160 MS Points)
• Melatonin - Silversun Pickups (160 MS Points)
• Pretty in Pink - Psychedelic Furs (160 MS Points) -Dammit - Blink-182 (160 MS Points)