One of those things that is dreded by any product manager is Service Outage and Maintenance Scedules. The moment when some users may access your product and goes back with a groan or even may send you a brickbat through the feedback system. One of the ways to tackle this is to tell each user in advance about the maintenance and down time or if it is a service outage then show them a message that will convert the dreaded groan to a smile.The maintenance pages shows the creativity of the product team and the manager.
My personal favorite has always been bloglines.
Here is a list of some good maintenance page implementations from Smashing Magazine.