http://www.freshmeat.net is a clearinghouse for opensource (although not limited to opensource) project announcements. You can also search Freshmeat 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.