Connotea 1 is a free online reference management and social bookmarking service for scientists created by Nature Publishing Group 2. While somewhat experimental in nature, Connotea already has a large and growing number of users, and is a real, fully functioning service 3. The label 'experimental' is not meant to imply that the service is any way ephemeral or esoteric, rather that the concept of social bookmarking itself and the application of that concept to reference management are both recent developments. Connotea is under active development, and we are still in the process of discovering how people will use it. In addition to Connotea being a free and public service, the core code is freely available under an open source license 4. Connotea was conceived from the outset as an online, social tool. Seeing the possibilities that del.icio.us 5 was opening up for its users in the area of general web linking, we realised that scholarly reference management was a similar problem space. Connotea was designed and developed late in 2004, and soft-launched at the end of December 2004. Usage has grown over the past several months, to the point where there is now enough data in the system for interesting second-order effects to emerge. This paper will start by giving an overview of Connotea, and will outline the key concepts and describe its main features. We will then take the reader on a brief guided tour, show some of the aforementioned second-order effects, and end with a discussion of Connotea's likely future direction.