Post fliers on bulletin boards at libraries, bookstores, community centers, coffee houses, senior centers and grocery stores. Include your name and phone number or e-mail address. Mention how many volumes the set contains, the condition and the publication date.
List your Britannica encyclopedias on local online classified sites such as Craigslist. Include your phone number for faster response times or request an anonymous e-mail address for replies.
List your encyclopedias on online auction sites such as eBay. As purchasers probably won't want to pay high shipping fees, specify that your books are available for local pickup only. This will also save you the trouble of packing up the books and taking them to a post office or shipping center.
Contact local arts and crafts groups and organizations to see whether they might purchase your encyclopedias. Explain that they can use encyclopedia pages in decoupage and collage projects, as wrapping paper or in myriad other crafts projects.
Sell your encyclopedias at a garage sale. Keep this as a last option, as people who frequent yard sales often look for bargains and are accustomed to haggling.