It shows you as many as you've got - in Traffic Sources > Referring Sites, at the bottom of the column of figures either click the arrow to show the next page, and/or click the drop down that tells you how many rows you are looking at, and choose to see up to 500 results at a time.
I found out that if you get the report via email that you can't see all the referrals. Does anybody know why this is and how it can be corrected?