A simple solution would be to make a special email address that you direct all your cron files to (via a MAILTO= directive).

At it's simplest you could then just have a webmail interface to the box, but that's a bit crummy. You could write a simple script that fetched all the mail and made a web page out of that data (or via a database/cgi, whatever works for you).

The advantage of doing it this way is that no change is required to the cron jobs other than adding the MAILTO directive at the top of the file. You could also direct the cron outputs from multiple machines to a central server.