I too use Quicken for accounting so I can categorize income/expenses as I go - then I just import the info into tax software when the time comes.

I use a combination Palm Pilot/cell phone (Samsung SPH-i500) to keep track of all other data including bookings, outstanding money, contacts, contracts and invoices. It's really a complete pocket office. I find having the phone and Palm as one unit very helpful because I often use my cell phone to confirm bookings and I need my calender and contacts close by at all times. I can even fax from it, browse the web and do email. It can display local weather radar in real time. I also have Quicken for my Palm Pilot so my accounting info is at hand, like all my data. The phone can even act as a high-speed modem for my laptop when I travel. Everything on my Palm is backed up to my computer daily. I haven't done it yet but I can even add a device so I can use my Palm phone and swipe credit cards for CD purchases onsite. My Palm phone is an essential part of how I do business.