Kids Domain at www.kidsdomain.com/index.html - lots of programs to download. Start by clicking on Language Arts (either PC or Mac), then select by age. Here are a few recommendations to start with:
Beginning and Intermediate
Intermediate and Advanced
Hot Potatoes - download at web.uvic.ca/hrd/halfbaked - free authoring program. You can easily make a wide range of exercises, including multiple choice with a reading (timed or not), crossword puzzles, gap-filling, and matching. You can use sound and graphics as well as text in these. The program turns your exercise into a webpage that students can use either on the Internet or just from a floppy disk. What's even better is to have the students create the exercises as practice for each other.