Red Hat.

Worked there as an intern during college, continued for few more years and returned there after a brief stint at a startup.

Work/life balance is great, most code public has so many advantages and colleagues are friendly and decent humans.

Some teams might be worse than what I experienced, but even if I was growing mildly frustrated (i.e. pressure from product people to push product out of hte gate before it was ready and I was one of hte damned QA people), the robust internal transfer system meant, I could just move to a team where I felt my contribution was more valued even from non-programmers ;)