Messaging Queue

  
I understand there is a Messaging Queue which is being for Asyn logging. Are they exposed to define any user defined queues for business scenarios we could use it. 
The queues are for logging only. They are avaiable for for you to take advantage of their asynchronous nature through the Custom Log. Take a look at http://www.outsystems.com/community/download.aspx?DocumentId=567. As the name implies, it is for logging...

You can always write an extension to access the queue by yourself. Usual  worries apply :)