Book Moot featured a post about sewing Regency gowns; In the Long Run shows you exactly how to make one; and Dress Diaries has uploaded photos of lovely modern examples of Regency dresses.
Sewing Central sells patterns circa 1800-1815.
Sense and Sensibility will let you sign up for an online sewing class for only $40.00
For more on this topic, go to the Jane Austen Centre's website and read Regency Dress for the Modern Occasion,
or The Great Pattern Review from The Greater Bay Area Costumer's Guild.