Full disclosure: I hate Dashboard. I have found very few widgets that do anything useful for me, and having them invisibly off in some weird dashboardy land bugs me, too. It pretty much limits me to widgets that I use infrequently enough that I don’t want them in front of me.
However, I just found a good one. ProdMe is a widget that beeps at you. It can be hourly chimes (a la MacOS 9), an egg timer, or an alarm clock. It can also notify you via Growl.
There’s lots of times that you need a timely reminder. In my case, it’s usually to check on a database restore or an exceptionally long software install/update. I just go to Dashboard, tell ProdMe to bug me in 30 minutes, and in 30 minutes I get a noise and a Growl notification reminding me to check on the server in question.
Very handy for those one-off reminders that you’d rather not burden iCal with. As for it being off in Dashboard-land, well, who cares? It’s a set-and-forget kind of thing, so it belongs there out of my sight.