Operation World is a book, CD, website and prayer movement for world evangelization. It contains information on the state of the church and evangelism in every nation on earth, and specific prayer needs for each.
There are many ways to pray for the nations using Operation World. You can go to their list of countries and choose a country to pray for. Not sure which countries to pray for? You can use their 60-day country list and commit to 60 days of prayer. Or you can use their 365 day Prayer Calendar with a region or country featured for every day of the year. Or you can buy the book and CD with the most comprehensive information available.