The Twilight Forest

So, I originally planned suggesting the forestry mod which I used alot in the FTB pack. But then I remembered this little gem!

The Twilight Forest mod allows you to explore a new world in the same fashion as the nether. Create a portal for the forest, which is a 2 by 2 grid of water surrounded by flowers, then throw a diamond in and you have access to the forest.

In the forest you have plenty of new places to explore, from giant necromancer's castles to catacombs protected by enemies straight out of Greek mythos.

Also, new items and treasure to loot too! But the reason I like is the fact its just so pretty at times. You can read up more about it on the wiki here:

http://twilightforest.wikispaces.com/

Well, that's my suggestion!

Oh yeah, I love this mod as well!!
Granted, this mod alone probably wont be able to carry us through the month, but paired with some other interesting exploration mods (like Biomes o Plenty, or Better Dungeons), and it would make for quite the mini adventure pack. ^^