http://developer.amazonwebservices.com/connect/message.jspa?messageID=112271

've had the same issue with a snapshot of a 4GB volume. I created a new 10GB volume based on the snapshot. 
After you mount it all you need to do (in my case on linux ubuntu) 
resize2fs /dev/sdh 10G 
Message was edited by: tombmurphy

The basic process to resize an EBS volume is:

1. Unmount it
2. Create a snapshot
3. Create a new volume from that snapshot with a bigger size
4. Recreate the partition table
5. Resize the filesystem
6. Mount the new volume and delete the old volume & snapshot

Some background I found while researching:

• http://www.linuxinsight.com/files/ols2002/dilger-reprint.pdf - Goes into excruciating details of how ext2/ext3 are laid out and a way to do a "live" resize. I didn’t need a live resize.
• man resize2fs : 
  "When recreating the partition, make sure you create it with the same starting disk cylinder as before! Otherwise, the resize operation will certainly not work, and you may lose your entire filesystem."
• Shrinking partition and also talks about resizing the boot partition from a Live CD:http://www.howtoforge.com/linux_resizing_ext3_partitions

Here is what I did: