Walmart offers the Straight Talk AT&T-Compatible SIM or Micro SIM Card for $3.99. Opt for Site-to-Store pickup to dodge the $4.97 shipping fee. That's $3 under last winter's mention and the lowest price we've seen. (It's a current price low by $12.)

Also available are the Straight Talk T-Mobile-Compatible SIM or Micro SIM Card for the same price. That's another low, this time by $2.