This week's Deal of the Week has three different XBLA games on sale for 400 points, for Xbox Live Gold members only.
World of Keflings
Worms 2: Armageddon
The DLC pack for Worms 2 is also availible at 50% off for just 200 points. Worms 2 has been on sale a few times previously but this is the first reduction for the other two and they are fairly recent releases, coming out around Christmas time last year.
Also, there is a seperate sale which is good for both Gold and Free (aka Silver) members which apparently runs till this Friday when there will be further items reduced for 1 day only. I've made a seperate deal for it here: http://www.hotukdeals.com/deals/xbox-live-marketplace-sale/908895