Purple Math
Purplemath: Converting Between Decimals, Fractions, and Percents
Scroll down to just below the middle of the lesson for an in-depth lesson on converting fractions to percents. Works through numerous examples step by step and shows what happens when the "decimal expansion" doesn't end when converting.
AAA Math
Aaa Math: Fractions to Percents
This tutorial explains how to convert fractions to percents and features practice exercises, games, and the like.
Other
Project Happy Child: Fractions and Percents
Miss Walker explains to Bart the fine details of the relationship between fractions and percents. At the end of the discourse is a link, "Free worksheets for percentages," where you can go to print off some practice sheets.