http://www.freshmeat.net is a clearinghouse for opensource (although not limited to opensource) projects. The front page contains announcements of new releases. You can also search the Freshmeat database or browse it by various categories, including programming language. You can also subscribe to particular projects, in which case you will receive email whenever a new release of the subscribed project is announced.
Subscribe to the Freshmeat newsletter to receive automated daily digests of the days announcements: http://www.freshmeat.net/newsletter/
Swik is another site for open source listings.