LIGO vacancies at Caltech, LIGO Hanford, and LIGO Livingston can be found at Caltech's job listings.
Caltech Notices of Intent can be found here.
LIGO vacancies at LIGO MIT can be found at MIT job listings.
If you are interested in working for LIGO at other collaborating universities, check your preferred partner-institution's job postings. For a list of collaborating institutions, see LSC Member Institutions.