I was always hesitant about doing a solo trip but I took the plunge in 2014 and now it's a must do as often as possible. My next solo trip will be early 2017.
The one thing I really enjoyed doing was playing Disney Transportation Roulette. If I didn't have any ADRs for the day I would leave the resort first thing in the morning and take the first bus that arrived and go to that park. When I was done there I would hop on the first resort bus that showed up and end up at whatever resort we came to. I would repeat this throughout the day until I felt it was time to head back to the resort. If the resort had other travel options, such as boats or monorail I would toss a coin to see what travel option I was going with. It was so much fun.
I got to see some resorts I had never visited before and it was so nice not having to make plans for everything. I can't wait to do it again 10 months from now.