So you just won a 1 day all expense paid visit to WDW. Only problem is you can't bring anyone with you. Where do you stay? What do you eat? What do you do?
I'd probably stay at the Contemporary so I could walk over to the Magic Kingdom. Then I'd have lunch at LTT and dinner at the Cali Grill. Maybe I should stay at BLT? Decisions. I'd probably only ride the low-maintenance rides like PotC and Haunted Mansion, so I don't have to stand in boring lines by myself.
OOoo, good question! I think I might stay at the Beach Club - easy access to Epcot and HS, the Boardwalk and a great pool. My day would be a trip to Epcot and HS, with swimming in the afternoon.
For food, I'd probably get fish & chips from the Yorkshire, and then eat ice cream, french fries (Beaches & Cream) and rice krispy treats for dinner.
Ohhhhhhhhhhhh..fun!
I would stay at BLT and hit up MK in the morning and maybe DHS at night to hit up ToT & Toy Story.
Bella
Grand Floridian, spa treatments, tea at the Grand for "lunch" and dinner at Victoria and Alberts...because when could I ever do all of that otherwise? 
I'm not even sure I'd make it to the parks, although if it were this time of year, I'd definitely head over to MK for all the holiday goings on...
I love to wander around Epcot when I'm solo in WDW. There's so much to see and explore. When you're with other people, sometimes you have to skim over the things that would be interesting to you.
May 2008 CSR 
I would seriously consider a nice stay in the Beach Club. Lunch in ESPN, dinner at Le Cellier. Walk around World Showcase all day.
Hi,
I've been to WDW eight times (1982; 2000; 2003; 2004; 2005; 2006 (twice); 2007). All but the first trip (with my high school class) were solo. If I waited for someone to go with me, I would never leave home.
My one-day solo trip would include a stay at the Polynesian. MK to ride Pirates of the Caribbean. AK for Expedition Everest. Lunch at Flame Tree BBQ. Then Epcot World Showcase for dessert @ the Norway bakery. Hollywood Studios to ride Tower of Terror and RnRC while praying I keep dessert down. Back to Epcot for Mission:Space and possibly Test Track (no time for Soarin'). Back to Polynesian for dinner @ 'Ohana, stagger to my room to end my day exhausted in a food coma.
Jim
All 4 parks in one day. I'd pass out!