My husband works as a QA (Quality Assurance = tester) for Eidos Interactive. Don't be discouraged, as they get many applications at every company. Some of his co-workers had to apply multiple times before getting an interview (of course don't spam your resume daily, that's obnoxious).
Most video game company websites have a link on their main page entitled Careers, Jobs, or something similar. If you don't see it, check at the very bottom of the page.
I've dug up a couple of links for you:
Eidos: http://tbe.taleo.net/NA4/ats/careers/jobSearch.jsp?org=vam&cws=1
EA: https://jobs.ea.com/
Ubisoft: http://jobs.ubisoft.ca/home.php?param=fr-CA
There are also companies like Babel, which handle outsourcing of QA:
http://www.babelmedia.com/