Document similarity measures are required for a variety of data organization and retrieval tasks including document clustering, document link detection, and query-by-example document retrieval. In this paper we examine existing and novel document similarity measures for use with spoken document collections processed with automatic speech recognition (ASR) technology. We compare direct vector space approaches using the cosine similarity measure applied to feature vectors constructed with various forms of term frequency inverse document frequency (TF-IDF) normalization against latent topic modeling approaches based on latent Dirichlet allocation (LDA). In document link detection experiments on the Fisher Corpus, we find that an approach that applies bagging to models derived from LDA substantially outperforms the direct vector space approach.