There are lots of vision improvement books, courses, audio books, charts, tools, you name it. Before you hand over your hard earned cash you can do a search on google for free information. On Google Books you can view the book that started it all – Better eyesight without glasses by W H Bates (the link will take you to a version that you can read online, for free). The book was a revolution – and a shock to the established ophthalmologists. It is strange however that they are still taught at college and medical school that eyesight cannot be taught naturally. Another great resource full of downloadable e-books and magazines about improving eyesight naturally is http://www.cleareyesight.info.
How else would you monitor the progress of your natural vision exercises than test them with the Snellen eye chart. There are many sites out there that have printable examples of this chart, but the best one I have come across is from I-See.org. This site has many versions of the chart, and the beauty of the thing is that it is free! The downloads section of the site has a printable PDF version of the chart as well as postscript. Enjoy!
Feel free to post other links and resources that you might find!