Seth Priebatsch

Two things you'll notice about Seth Priebatsch: One, his infectious, get-you-out-of-your-chair enthusiasm. Two, the inventory of entrepreneurial feats he's managed to accumulate at a remarkably young age. The 21-year-old founded his first startup at age 12, and by age 18, he'd founded another -- PostcardTech, which makes interactive marketing tours for CD-ROM. [+]