Astrophysics:


AIfA
COSMOGRAIL
Polarisation (COST Action)
NASA Extragalactic Database (NED)
MAST archive database
The Master Lens database and Orphan Lenses Project
CASTLE database of lensed QSOs
GAVO data center
ESO archive query form

Online tools:


Ned Wright Cosmology Calculator
Flux conversion
ESO Calendars and calculators
RA-DEC flexible converter