Originally Posted by
Eladrin
The outdoor adventure areas (like the Cerulean Hills through the Vale of Twilight) are extremely popular for solo play, and were designed primarily for solo or small groups as well as for people that seek persistent progress in variable length play sessions.
Virtually all of our dungeons up through level six outside of the quest chains have a "solo" difficulty available - by level six, we found that most solo players preferred playing on the "normal" difficulty setting.
There's quite a bit of solo content in DDO these days.