Who’s eligible:
Anyone under age 65 can contribute to an HSA if they buy a high-deductible health insurance policy. The policy’s deductible must be at least $1,000 for individuals or $2,000 for families.

Pros:
» Contributions are tax-deductible, even if you don’t itemize.
» Portable; Like an IRA, it travels with you, not your job.
» Rolls over each year, unlike a Flexible Spending Account.
» Earnings grows tax fee (also like an IRA).
» No taxes on withdrawals used to pay healthcare expenses.
» Possible to invest in mutual funds to boost long-term returns
» Some companies match contributions to HSAs, like others to 401ks.
» HSAs are inheritable.

Cons:
» You’ll have to pay for everything (at least partially) out-of-pocket, including things like routine visits and prescription meds that you may not have been used to paying for.
» High-deductible health insurance means you have to have money on hand to cover the whole amount if needed.
» Best suited for young and healthy people, if you usually max out your benefits a lower deductible is probably best for you.
» You are limited to certain HSA providers.
» The account and maintenance fees can be high, some don’t let you invest in stocks.
» Watch out for exclusions of pre-existing conditions in the policy.
» Since these have only been around since 2004, there isn’t quite as much competition as would be ideal for a consumer.

How much can I put in?
You can contribute up to the amount of the deductible to an HSA, but no more than $3,050 for individuals; $6,150 for families. And you can add an extra $500 if you were born before 1950 to help with health care costs in retirement.

* Individuals age 55 and over may deposit into their account (and take a tax deduction on) an additional catch-up contribution of $1,000 in 2010.  

Here's some helpful info in determining which company.
Cigna offers coverage for preventative care, Blue Cross Blue Shield does not. However the Cigna premium is usually higher as a result of the extra coverage.