Some shoppers use Microsoft Excel, and I believe there's a Mac compatible version, icXL. My method is a 3-ring binder; obviously manual, but it works for me. Flash is the Excel queen.
No EIN - we've been told it can raise eyebrows with the intent of separating you from your money, or at least making your life more *interesting*.
No, I don't file quarterly. Complete a Schedule C with your 1040. YES, keep track of mileage. The IRS allows .55/mile for 2009, very generous and helps to offset income. Other expenses are deductible as well, some may have to be pro-rated.
While searching here for discussions on tax ramifications and record-keeping, they may be hidden in an unrelated thread. We often digress