We all used it as a way to learn about what had just come out, and discover new useful projects by watching/browsing interesting looking items on the feed. All it really was is an aggregator of update feeds... So lets build a new (RSS) aggregator/planet and reach out to the old Freshmeat projects/users to get them to move over?
If the functionality is pared right down it shouldn't even need logins or any of that stuff. Just make RSS links clearly visible and say to people "hey if you want to follow this project specifically, here's the link for your RSS reader!".