I was asked in the comments on a previous entry if the desktop alert display interval could be customized to longer than 30 seconds. The UI in Outlook 2003 (Tools | Options | Email Options | Desktop Alert Settings) limits you to 30 seconds, but yes you can configure the interval to be longer using the following registry key:

HKCU\Software\Microsoft\Office\11.0\Common\DesktopAlerts
DWORD: "TimeOn"

The decimal value is in milliseconds, and it's additive on top of 3000 milliseconds. So for example, if you want a 4 second delay, set it to 1000 milliseconds (3000 ms + 1000 ms = 4000 ms = 4 seconds).  Make sure to select 'decimal' in the regedit UI. For a 60 second delay, the value would be 57000 milliseconds.

Outlook does not need to be restarted after changing this setting. If you set it > 30 seconds, the UI in the desktop alert settings dialog will still display 30 seconds but the desktop alert will actually display the appropriate length of time.

As always, be careful when mucking with the registry! :-)