To open or contribute to an HSA you must meet certain eligibility requirements. Specifically:

You must be covered by a qualified high deductible health plan on the first day of the month
You cannot be covered by any other health plan that is not a qualified high deductible health plan, including spouse’s health insurance
You cannot be covered [...]

HSA contributions are based on your insurance coverage and age. For 2009 the limits are:

Single accounts (only one person covereed on the health insurance policy)—$3,000.00
Family accounts ( multiple people covereed on the health insurance policy)—$5,950.00
Additional contribution for account holders who attain age 55 by December 31, 2009—$1,000.00

Contribution tips:
It’s not too late to make 2008 contributions. [...]

In Administrative, Procedural, and Miscellaneous Notice 2004-50, the IRS addresses this question. See Questions 2 and 4, excerpted below:
 Q-2. May an otherwise eligible individual who is eligible for Medicare, but not enrolled in Medicare Part A or Part B, contribute to an HSA?
 A-2. Yes. Section 223(b)(7) states that an individual ceases to be an eligible individual [...]

Some of our account holders have asked about the security of their HSA money invested in the Vanguard Prime Money Market Fund. Vanguard has issued a statement confirming their continued participation in the Treasury Guarantee Program. You can get details by following the link below:
Vanguard money market funds participate in extension of Treasury Guarantee Program

There are essentially four “Concierge” models:

Fees for care. In this model the fees charged are directly related to medical care, as described by the IRS, and would generally be considered as eligible medical expenses under the HSA guidelines.
Annual Physical. Here a fee is charged for an annual physical, usually comprehensive in scope, that includes no [...]