By singles, what do you mean?
There are trips geared to solo travelers but they are divided by demographics to some extent. There are also trips that are geared to single women specifically.
Most of the guided tours attract solo travelers because it is easy to make friends along the way even if some people are coupled. Often they will pair you up with another person to avoid the singles supplement. The days are over when these kinds of tours were solely for people who wanted to see Europe in 7 days. My friend (male) did a guided tour through Vietnam and Laos last year.
Other good bets are tours involving some kind of activity. When I rode, I did a riding vacation by myself through Equitour.
Some days I pray for Silence, Some days I pray for Soul,
Some days I just pray to the God of Sex and Drums and Rock 'N' Roll.