Virtual Observatories, Interoperability

General 

SPASE (Space Physics Archive Search and Extract)
IVOA (International Virtual Observatory Alliance)
IPDA (International Planetary Data Alliance)
OV-France (Support program for VO development in France)
EURO-VO (The European Virtual Observatory EURO-VO)

Space physics 

NSSDC-VO-Portal 
VHO (Virtual Heliopsheric Observatory)
VMO-NSSDC (Virtual Magnetospheric Observatory, NSSDC)
VMO-UCLA (Virtual Magnetospheric Observatory, UCLA)
VSPO (Virtual Space Physics Observatory, includes a searchable registry)
VITMO (Virtual Ionosphere Thermosphere Mesosphere Observatory)
GAIA (VO for ground data)

Solar Physics 

VSO (Virtual Solar Observatory)
EGSO (European Grid of Solar Observations)
SSVO (UK Solar System Virtual Observatory)

Planetology 

Europlanet
Europlanet Plasma Node (Plasma node in Europlanet/Idis)