These days my commute isn't too lonely, especially in the afternoon/evening. Dunno if it's the cool weather or the lack of MUP traffic, but I strongly prefer late fall and early spring commuting. Gives me more time to be "lonely". There are some other year-round commuters I see fairly regularly; we usually exhange a friendly nod. Otherwise, when I'm alone on my commute I look for wildlife (squirrels, geese, etc.) or just enjoy the scenery if conditions don't require more attention.
I'm one of those guys who's happy not to have to talk all the time and can also honestly answer at times that I'm not thinking about anything. I like to get into this state on my rides when I can.