Keeping records on expenses for tax purposes

[Jeff Howard]

All,

Quick question... Building a spreadsheet of all my expenditures for my rental property.  What kind of data does the IRS want to see if I ever get audited?  I assume a list of the expenditures with dates, I also assume I have to have a receipt for every last thing, what about driving miles to and from the location?  How do I prove that?  Is there good software out there that captures this for you?