We describe “digitometric” services and tools that add value to open-access eprint archives using the Open Archives Initiative (OAI) Protocol for Metadata Harvesting. Celestial is an OAI cache and gateway tool. Citebase Search enhances OAI-harvested metadata with linked references harvested from the full-text to provide a web service for citation navigation and research impact analysis. Digitometrics builds on data harvested using OAI to provide advanced visualisation and hypertext navigation for the research community. Together these services provide a modular, distributed architecture for building a “semantic web” for the research literature