There is no maximum personal injury award.
There is a maximum when it comes to general damages. General damages are compensation for pain and suffering and loss of enjoyment of life (past, present and future). The maximum is $326,244 as of May 2008. This number is indexed for inflation.
In car accident claims specifically, you can only get 80% of your net past loss of income. For all other types of personal injury claims there is no such reduction in the past loss of income claim.
In a personal injury award there is no maximum for any other type of award of damages. An explanation of the types of awards in a personal injury claim can be found in an earlier blog entry: What compensation can I get for my personal injury claim?
There is a practical maximum to the personal injury award. It is unlikely you will get more than the insurance limits of the person you are suing, unlikely but not impossible.