I'd start off with 2-3 sets of rechargable batteries and a charger, an A/C cable and a cigarette lighter cable. There's TONS of antennas out there available from RS and other makers (personally I prefer the 800 mhz Radio Shack antenna and the Icom UHF/VHF flexible antenna) Also definately a 9 Pin to Stereo cable, and Win95.
I would also recommend this:
http://www.davee.com/scanrec/ It's free, but you need a 1/8 inch to 1/8 inch stereo cable. Just plug one end into the scanner headphone jack and the other into your computer's line in jack. It'll record anything you want to listen to, only when the SQ is broken. I've grown to find it pretty handy lately.