Letters sent by Abraham b. Yiju are accessible from the Cambridge Digital Library's Cairo Genizah Collection as well as the Princeton Geniza Lab.
A rich discussion about Jewish merchants and travelers, including Abraham b. Yiju is available from the National Library of Israel.
The mapping of Ibn Battuta's travels and additional information is available from this website by UC Berkeley.
The autobiography of Sayyida Salme, aka Emily Ruete is available from the Library of Congress.