Ask Slashdot:Open Source Program Databases

Gregory Seidman wrote in to ask " I would like there to be a public (web) database of open source programs searchable by task/niche in particular." I can think of several, but I'm curious what people's opinions are of these. Some are fairly comprehensive, others are easy to use. Is there a clear winner? There are gold nugget applications out there, but so often they are things you stumble upon... it would be nice if they could be found simply.