New Ubuntu EC2 Instance things to remember

if you want to attach an existing EBS volume to the instance, make sure it's in the same Availability Zone (like "us-east-1c")

To SSH at all:
download that private key that they make you create as part of the setup console
ssh -i (thatkey.pem) -l ubuntu
(there's one user created at the start, called ubuntu)
sudo adduser dantasse
sudo vim /etc/group # and add dantasse to sudo group
sudo vim /etc/ssh/sshd_config # and set PasswordAuthentication to yes
sudo /etc/init.d/ssh reload
Now you should be able to SSH.

Attach the EBS volume on the AWS console. For example, attach it as /dev/sdf. Because it's Ubuntu, it will be attached as /dev/xvdf instead. (because reasons :P) You have to mount it still, though. Say you want to mount it at /data:
sudo mkdir /data
sudo mount /dev/xvdf /data