It's difficult to quote an average across the board, but here's the three major debt offenders and their respective numbers:
Credit Card Debt:
When it comes to the average person's credit card debt, the classic figure is in the neighborhood of $9200 per household. Assuming an average of two adults per household, that would make the average $4600 a piece.
That is in fact just an average however, based of widely used figures provided from CardWeb. Bear in mind that using an average means those with excessive credit card debts skew the figures for the average household.
Speaking of averages, between banks and retail stores there's more than 6 credit cards issued out there for each consumer, and the average balances carried on those cards has more than doubled over the last decade.
A home loan is most definitely a debt, but because the home is an asset as well it's often not considered as such. Recent low interest rates have seen more people buying properties than ever, making it next on the list for the bulk of America's personal debt. The average principal amount owed on a home loan is nearly $70,000, with 20% or so of mortgagers owing more than $100,000.
In the year ending 2000, 60% of students graduating with a bachelor's degree took out a federal student loan, with an average debt of more than $16,000 according to the National Center for Education Statistics. There are also significant amounts of private loans related to education, and cumulatively recent studies show the average student is left with a debt of $20,000 or more after graduation.