Free books, posters, product samples, films, services and other resources are available for the asking. While some freebies are for fun and others are money-savers, they're all interesting and useful. Be sure to include a self-addressed, stamped envelope or a small postage-and-handling charge if the offer calls for one. Allow them for your request to be processed and mailed. Let the companies or organizations who provide freebies know how useful you've found these items. EYE SEE

Eyes are remarkable windows to the world. They do a job no machine has yet duplicated, and they do their work with minimal attention from the owners.

The American Optometric Association offers a free set of materials that includes a diagram of the eye and two booklets. "About Sunglasses" should come in handy these summer days. It tells you what to look for - and look out for - when buying sunglasses. "Contact Lenses" is a 10-page booklet discussing both hard and soft contacts, for those whose vision is no longer 20/20. You'll also receive a copy of "What is an Optometrist," and a 3"-by-6" reminder from Seymour Safely about protecting your eyes. The latter should be up on the kids' bulletin boards.

These materials are available free by sending a long, stamped (28 cents), self-addressed envelope to Communications Division, American Optometric Association, 243 N. Lindbergh Blvd., St. Louis, Mo. 63141. READERS WRITE

Q - My wife and I have saved enough money for the down payment on a new home. Are there any freebies that could give us home-buying advice?

A - Before plunking down your hard-earned money on a dream castle, ask for a copy of "Buying Your Home." A 13-page introduction to the grim realities of buying such as contracts, financing, title and closing, it might just keep the castle from crumbling before your eyes. This is a case where a little bit of prevention can prevent the need for a very expensive cure. Free if you send a long, stamped, self-addressed envelope to Buying Your Home, American Bar Association, 1155 E. 60th St., Chicago, Ill. 60637.