You can fly into Savannah's airport, which is about an hour from Hilton Head, but then you absolutely must have a car to get around.
Hilton Head Island Airport is served by US Airways Express. Most travelers use the Savannah/Hilton Head International Airport, less than an hour from Hilton Head, which is served by American Eagle, Continental Express, Delta, Northwest, United Express, and US Airways.
The Lowcountry Regional Transportation Authority has a bus that leaves Beaufort in the morning for Hilton Head that costs $2.50. Exact change is required. This same company has a van that, with 24-hour notice, will pick you up at your hotel and drop you off at your destination for $3. You can request a ride weekdays 7 AM to 10 AM or 12:30 PM to 3 PM.
At Your Service and Gray Line Lowcountry Adventures are good options in Hilton Head.
Hilton Head Island Airport (120 Beach City Rd., Hilton Head, SC. 843/689-5400. www.hiltonheadairport.com). Savannah/Hilton Head International Airport (400 Airways Ave., Savannah, GA. 912/964-0514. www.savannahairport.com).
The Lowcountry Regional Transportation Authority (843/757-5782. www.gotohhi.com/bus).
At Your Service (843/837-3783). Gray Line Lowcountry Adventures (843/681-8212).