I've discovered the best tracts are ones that illustrate (using pictures) how to be saved. People tend to pay more attention to pictures than reading words.
My favorite tract and the one I use the most is Billy Graham's Steps to Peace with God. Along with being a crystal clear Gospel presentation, its also the most expensive. They're $5 plus shipping for a package of 25. (Click here to order).
This tract is a simple picture story about how a person can be saved. I use Steps to Peace with God will every person who accepts Christ at First Baptist Moreland - adults, students & children. Even someone who can't read can understand the Gospel with this resource. I highly recommend it, but for mass distribution, it can become expensive.
If you're passing out hundreds or thousands of tracts at a special event, I recommend the Fellowship Tract League. Their tracts are all free, they only ask you pay for shipping. I recently ordered 1,200 child-friendly tracts for our upcoming Trunk or Treat. I paid $5.80 for shipping. They have hundreds to select from in multiple languages. I prefer to call and place an order (compared to online) - I explain to them what event I'll be distributing at and they recommend the best ones. I'm very thankful and grateful for their tract ministry. Since 1978, they've printed over four billion tracts and have never charged for one.
Here are two other companies that provide a variety of tracts, typically each package of 25 is $2.50 plus shipping.
Crossway Tracts - they have outstanding designs
Tract Planet - they sell the famous $1,000,000 bill
Along with tracts, I give away Bibles. The most affordable and easy-to-read Bible (Old and New Testaments) I've found is the HCSB Outreach Bible from LifeWay. Last year, FBC Moreland gave away 1,200 of these to every home in our zip code and 2013 is the year of the Bible for the North American Mission Board. (They cost $1.25 each when you order a case of 36 - click here to order).