Power Search was a real useful feature and there is now good reason why Apple decided to ditch/hide in iTunes version 11. But luckily you can bring it back quite easily. Check it out.
If you are a heavy twitter use, possibly with more then one account, than I suggest you to give Tweetdeck a try. You can arrange, schedule, monitor and manage your tweets with ease.
A short questioner where you will test your basic knowledge of the Gimp image manipulation program. Have a go at it and build up your knowledge profile stats.
If you experience an Mac OS X program to freeze and you cannot exit it by clicking quit or using a keyboard shortcut, you can always force it to quit using the Activity Monitor.
An interesting video where a guy explaining why he believes that we have landed on the moon and tells also about waving flag, shadows and everything else.