This page gives a brief overview of useful medical visualization datasets that are freely available online.

No registration required:

• Erlangen Volume Library – diverse datasets, including DTI.
• Dr Gordon Kindlmann’s brain – high quality DTI dataset of Dr Kindlmann’s brain, in NRRD format.
• OpenfMRI.org – a project dedicated to the free and open sharing of
  raw magnetic resonance imaging (MRI) datasets.
• OASIS – The Open Access Structural Imaging Series (OASIS): starting with 400 brain datasets.
• Osirix DICOM datasets – a rich collection of high resolution radiology datasets all in DICOM format. (update: unfortunately Osirix now requires a premium membership)
• Utah SCI CT datasets archive – collection of CT datasets, including micro-CT, at the Utah Scientific Computing and Imaging Institute
• VolVis.org dataset archive – collection of miscellaneous datasets, mostly in RAW format, focused on volume visualisation. (update: unfortunately no longer around!)

Registration required:

• National Cancer Imaging Archive – amongst other things, a CT colonography collection of 827 cases with same-day optical colonography.