Its demise was predicted so many times that some people actually believe the Dashboard is already dead. Fortunately it's not and Apple keeps including it in every release of OS X.
Personally, I find the application very useful and not a day goes by that I don't check one or another thing using one of the widgets I have installed, even though I don't use many.
Mac.AppStorm has compiled a really nice list of useful widgets for OS X's Dashboard. There's something for everybody's taste in there; I'm using the currency converter and iStat Pro. It also helped me remember the Color Burn Widget which I lost during an OS upgrade.
There are two widgets I'd like to add to that list, though:
Oh and everybody always forgets about the built-in widgets, so; multiple weather widgets, a few world clocks and the unit conversion widget never leave my dashboard.