Registries
Registries are "archives of archives" -- a registry allows you to query for archives and services. Most registries synchronize their contents, so you can choose any depending on your taste. Also, many VO tools come with integrated registry interfaces.
- The US-NVO's registry -- locate resources by keyword.
- US-NVO's DataScope -- locate resources by position
- The Euro-VO registry -- use ADQL to locate resources
Individual VO Nodes
- SkyQuery at Johns-Hopkins-University, Baltimore, USA
- SkyServer by the Sloan Digital Sky Survey (SDSS), USA
- US-American Virtual Solar Observatory (VSO)
- SkyView at NASA's Goddard Spaceflight Center (GSFC), USA