Individuals and Health Savings Accounts
The benefits of investing in a Health Savings Account have become apparent over time. More and more people are moving towards HSA plans for the advantages they offer account holders:

Tax Deductible Contributions
May be eligible to claim contributions on Federal Tax Returns (even if you don’t itemize)
Interest and Other Earnings on Health [...]

The following is from Kiplinger’s Personal Finance magazine (Nov. 2007):
BEST HEALTH SAVINGS ACCOUNT FOR INVESTORS
Health Savings Administrators
HSA Resources Bank
With an account from Health Savings Administrators, you can build a portfolio with 21 low-cost Vanguard mutual funds. And you can invest immediately, instead of waiting to accumulate a large balance.