I have mostly gone solo on all my WDW trips, however, as Teresa said, I have met up with many wonderful DISsers on each and every trip and have never truly been solo.
When by myself I love to enjoy my resort as much as I can, swimming, lounging with a good book, eating at the restaurant, etc. I also enjoy going to the parks and taking in the shows and stuff that I don't normally get to when I am with a group of people. I also LOVE LOVE LOVE wandering around world showcase at Epcot and taking in the shops, shows, food and any rides in that area. If you love Animal Kingdom (as much as I do), take in the trails where you will find animals lounging about in some really nice "habitats". Take a ride on Expedition Everest through the single rider line and have almost no wait. There are several rides that have single rider entrances at the various parks. For dining, I tend to gravitate to the bars that are at most of the nicer restaurants where you can find a full menu and friendly people to chat up.
Some Favorite:
Tune Inn Lounge (next to 50's Prime Time at DHS) - Home cooking and friendly bartenders.
Fulton's Crab House (Downtown Disney) - Awesome seafood and fish, Lovely atmosphere.
Jiko (Animal Kingdom Lodge) - Delicious food and a beautiful setting
There are many others but these are favorites of mine.
Also, not sure if you would be interested but we have a large group of singles/couples that go every May. This year's trip is May 13 to 18. Some of us are staying at the Boardwalk. We range in age from late 20s to 60s (I know, wide variety but ya know. . .lots of fun). There is a thread on here that I will find the link for and post.
All, in all, have fun on your trip and enjoy. You will love it.