For a limited time, ThinkGeek takes up to 58% off select t-shirts with prices starting at $9.99. Shipping adds around $7 depending on your zip code, or is free on orders over $75. Some best bets are the pictured I Recycle T-Shirt, which drops from $17.99 to $9.99, a price low by $5, or this Doctor Who Linear Tardis T-Shirt, which drops from $18.99 to $14.24, a price low by $4. Check out the other shirts available here. There is no sales tax (except OH, VA, and CA).