This paper describes a creative alternative for topic modeling:  mixed-membership on a "counting grid." The advantage of this approach  seems to be that you can move smoothly across the grid, achieving a 
high effective number of topics while the spatial smoothing prevents  overfitting. The disadvantage seems to be that there are more  parameters (grid dimension and size, and window size). A variational  inference procedure that is somewhat to LDA is possible, although no speed/complexity comparisons are provided. The spatial nature of the  approach has potential advantages for visualization as well.