This site's purpose is to help potential Debian contributors to find packages they'd like to work on.
The full list of packages in need of work (orphaned being-adopted for too long, RFA'd, or RFH'd) is at debian.org, but it's so long that it's tedious to scan it manually.
Wouldn't it great to be able to eg. see only packages that are implemented only in a given language or packages from a given upstream? This is exactly what this site aims to do, with a little help from debtags. (See the full debtags vocabulary).
The code behind this site, available at alioth, is also useful for running more complex debtags-based queries.