Introduction - If you have any usage issues, please Google them yourself
lda is a Latent Dirichlet Allocation (Blei et al., 2001) package written both in MATLAB and C (command line interface).
This package provides only a standard variational Bayes estimation that was first proposed, but has a simple textual data format that is almost the same as SVMlight or TinySVM.
This package can be used as an aid to understand LDA, or simply as a regularized alternative to PLSI, which has a severe overfitting problem due to its maximum likelihood structure.
For advanced users who wish to benefit from the latest result, consider using npbayes or MPCA: though, they have data formats different from above.