arXiv for open-access pre-(post)-prints of academic papers

Connected Papers  similar to Litmap and ResearchRabbit,  for visualising links between academic papers 

NASA/ADS  online database of astronomy and physics papers (really useful to export citations and create shared folders)

AAS Job Register

EAS Job Directory

  https://www.jobs.ac.uk/ 

How to write a cover letter for research jobs 

ESA Sky

JWST Science Archive 

LOFAR 

Emission line ratios

Rest frame emission line wavelengths