There are pages like this on Terraria Online, but not everyone here is also a member over there, so I thought I'd post some locations where you can find some information and teasers regarding upcoming PC updates.  <--- The official Terraria IRC.  This is the most active of the Terraria chatrooms; it is where most of the spoilers in the official thread come from these days. <--- Redigit, Cenx (Red's significant other), and several other important people from the Terraria community can be found here occasionally.  <--- Go here, download mumble.  IP for the public Terraria server set up by Cenx is, port is 8683.  I believe this one is mostly for chatting with people.  I haven't been on myself, so I don't know if spoilers are dropped here or not.

If you don't feel like joining a chat or if you just want to know what has been revealed so far, then you can find a compiled list of everything Red has hinted at or outright confirmed here or here.  Large pieces of news (usually complete with pictures) posted by Red himself can be found at the Dev Blog.