This document discusses tag-based information retrieval using folksonomies. It describes how folksonomies allow for tag-based browsing and retrieval of user-generated content. Several algorithms for folksonomy-based information retrieval are summarized, including FolkRank, which adapts PageRank to folksonomies, and GFolkRank, which extends FolkRank to account for grouping of resources. The document also discusses personalized variants of these algorithms and evaluates their performance on real datasets.