The city of Charleston [1] strictly regulates the treatment and upkeep of carriage horses, so there’s not a heck of a lot of difference in service or price among the various tour companies. Typically rides take 1–1.5 hours. They sometimes book up early, so call ahead.
The oldest service in town is Palmetto Carriage Works (40 N. Market St., 843/723-8145, www.carriagetour.com [2]), which offers free parking at its “red barn” base near City Market.
Another popular tour is Old South Carriage Company (14 Anson St., 843/723-9712, www.oldsouthcarriage.com [3], $20 adults, $12 children) with its Confederate-clad drivers.
Carolina Polo & Carriage Company (16 Hayne St., 843/577-6767, www.cpcc.com [4], $21 adults, $13 children) leaves from several spots, including the Doubletree Hotel and their Hayne Street stables.
Links:
[1] http://www.moon.com/destinations/charleston-savannah/charleston
[2] http://www.carriagetour.com
[3] http://www.oldsouthcarriage.com
[4] http://www.cpcc.com