For some reason which I can not fathom, both the Minecraft and Terraria News pages are not RSS capable. Thanks to Feed43, I bring you the RSS feeds for both! Just plug the below feeds into your favourite RSS reader and away you go.
Minecraft – http://feed43.com/1075277536157867.xml
Terraria – http://feed43.com/5177412023708415.xml
Let me know if you run into any issues.