Daniel Halan has developed an MSMQ Viewer for NServiceBus:
I've lately been working with a scalable cloud solution, and then it's good to use a Service Bus for sending commands, events and messages around the network. Now I tried few MSMQ message viewers that are available, but they all lacked the real-time feedback that would be nice when debugging or just want to know what is happening behind the scenes. So from that a new small application grew, called "ServiceBus MQ Manager". It's a small application that will monitor queues with a set interval, and present the Events, Commands and Messages that are there, but also keeping messages that has been retrieved (deleted) from the Queue.
which you can download through a link on his blog.