Talking to a biking enthusiast friend today and he told me of an alternative to buying improved tires or puncture-resistance tires or those grande-expensive kevlar sleeves.
What he did was take some Venetian blind slats, left them in the sun so they got soft and really bendy and then placed them into his tires making a cheap anti-puncture armor. He says he hasn't had a puncture since '98. You just have to use the right size slats for your tire size.
So there you go.