PhysioNet offers free access via the web to large collections of recorded physiologic signals and related open-source software. The PhysioNet web site is a public service of the PhysioNet Resource funded by the National Institutes of Health's NIBIB and NIGMS. About 45,000 visitors use PhysioNet each month, and the main PhysioNet server at MIT supplies about 4 terabytes of data (about 8 million hits) each month.
For an interactive self-guided tour, try PhysioTour. For a longer introduction, see About PhysioNet.
PhysioNet's collections of physiologic signals, time series, and images and relevant open-source software are described in An Introduction to the PhysioBank Archives and in An Introduction to PhysioToolkit. PhysioNet's tutorial library may be useful for getting started on a research project, and the PhysioNet FAQ contains answers to many common questions.
Additional background about PhysioNet may be found in these articles:
G.B. Moody, R.G. Mark, and A.L. Goldberger. PhysioNet: a Web-based resource for the study of physiologic signals. IEEE Eng in Med and Biol 20(3):70-75 (May-June 2001).
A.L. Goldberger, L.A.N Amaral, L. Glass, J.M. Hausdorff, P.Ch. Ivanov, R.G. Mark, J.E. Mietus, G.B. Moody, C.-K. Peng, H.E. Stanley. PhysioBank, PhysioToolkit, and PhysioNet: components of a new research resource for complex physiologic signals. Circulation 101(23):e215-e220 [Circulation Electronic Pages; http://circ.ahajournals.org/cgi/content/full/101/23/e215]; 2000 (June 13).