Simon, my flagship Mac app to monitor websites and servers for changes or failures, has been updated to version 2.5.7. It includes just a couple of changes, but is a recommended update for everyone:
Please note: version 2.6, currently scheduled for release in July, will require Mac OS X 10.5 (Leopard) as a minimum OS. So (unless there are any further bug-fix releases) this will be the last version that supports Mac OS X 10.4 (Tiger).