Updated project metadata. Mass spectrometry-based proteomics data, obtained experimentally or via public repositories, remains challenging to analyze. This challenge is particularly felt when re-analysing or re-purposing public data sets, endeavours that otherwise hold great potential. PeptideShaker is an open source system that greatly simplifies the interpretation and dissemination of proteomics data, and that automates the re-analysis of public data, thus completing the proteomics data cycle (http://peptide-shaker.googlecode.com).