With the news that Mt.Gox is going to be supporting Litecoin shortly, you might want to consider holding onto your Litecoin.  There is a big chance that price could spike in a very large way once it's listed.

As for Feathercoin's, convert them to BTC or LTC if you don't want to risk big losses.

I have 30x 5870's and they have 1 GB of ram each.  They mine at ~430 kh/s each and don't use any more than 500 MB of their dedicated memory.