Rev. Rul. 2005-25 (via Benefitslink.com) answers two questions:
(1) Is a married individual eligible to contribute to a Health Savings Account (HSA) if the individual’s spouse has non-HDHP family coverage that does not cover the individual? Answer: An individual who otherwise qualifies as an eligible individual does not fail to be an eligible individual merely because the individual’s spouse has non-HDHP family coverage, if the spouse’s non-HDHP does not cover the individual. Accordingly, that individual may contribute to an HSA.
(2) If the individual is eligible to contribute to an HSA, what is the maximum contribution limit? Answer: The maximum amount under section 223(b) that an eligible individual may contribute to an HSA is based on whether the individual has self-only or family HDHP coverage.