HELP!!! I was upgrading from ubuntu 10.10 to 11.4 when had a power outage. Now I cannot boot..Someone please help me with commands to get my system up and running again.

Are there any error messages? Does it boot to a terminal prompt of any sort?
If you have any really important data I would boot with a live CD and see if you can mount the drives. Save the data to an external drive.
You might need to reinstall but do not format the partitions.