It took me a while to shrink my EBS volume, but this post helped quite a lot. For further reference, this are the exact steps i’ve performed:

1. Created a snapshot of the EBS volume, for backup reasons.
2. Added a new volume, based on the snapshot.
3. Added another volume with the desired size.
4. Attached both, the Normal and Shrunken volumes.
5. Check the big volume, and resize it:

   e2fsck -f /dev/bigvolume
   resize2fs -M -p /dev/bigvolume
   ```- Note that 'resize2fs' will say something like:

   Resizing the filesystem on /dev/xvdg to 1035624 (4k) blocks.

   - Let's calculate how many 16MB blocks we'll need:

   x = 1035624 * 4 / 1024 / 16 = 253

   - Proceed copy'ing blocks to the small volume:

   dd bs=16M if=/dev/bigvolume of=/dev/smallvolume count=253

   - Resize + Check the small volume:

   resize2fs -p /dev/smallvolume e2fsck -f /dev/smallvolume

   - Stop the instance.
   - Detach the 3 volumes: Root, Big and Small.
   - Attach the *Small* volume at the same location as the previous root volume was. In my case, /dev/sda1.
   - **Ready!**