President Bush signed the Health Opportunity Patient Empowerment (HOPE) Act of 2006 on December 20, liberalizing the rules surrounding the use of Health Savings Accounts (HSAs). The major points in the new law are:

Through 2011, employers can rollover unused Flexible Spending Account (FSA) and Health Reimbursement Account (HRA) monies tax-free into HSAs, eliminating the 'use-it-or-lose-it' limitations of those accounts.

The rollover amount may be over and above the annual contribution level for that year
The amount is limited to the balance on the account being transferred from at the time of transfer or 9/21/2006, whichever is less
Only one transfer per FSA or HRA account
The individual must remain eligible (ie. employed and in the high deductible plan) for twelve months following the transfer or the transferred amounts will be included in taxable income and subject to 10% penalty

The HSA contribution limits for 2007 were increased to $2,850 and $5,650 for individual and family coverage respectively. Previously, contributions were limited by the underlying high-deductible plan's deductible amount.
Contributions limits are no longer pro-rated if the employee is not in the plan for the entire calendar year (eg. she was a new hire or the plan year started in a month other than January). This comes with a caveat however: if the participant does not remain eligible in the next year, any amount in excess of the pro-rated amount will be included in income and subject to 10% penalty.

Example: An employee joins the firm and enrolls in the high-deductible plan as an individual in May 2007 and quits on April 30, 2008. Under the old rules, she would only have been able to contribute $1,900 (8/12 * $2,850) despite being subject to a full $2,850 deductible. Under the new rule, she can contribute $2,850, but, because she did not remain covered for all of 2008, $950 ($2,850 - $1,900) would be subject to taxes and penalty.

Employees may make a one-time transfer from their IRA to their HSA

Limited by the annual contribution amount
Must be a trustee-to-trustee transfer
IRA withdrawal not included in income or subject to penalty but the deposit to the HSA is not eligible as a deduction either

Contribution limits will be subject to indexing at March 31 instead of August 31
Employers are allowed to make larger contributions on behalf of lower-compensated employees than before

As they are triple-tax free (contributions are tax deductible, earnings and withdrawals for qualified expenses are tax free), HSAs can be a powerful tool to save for future health care, long term care, and retirement.