Method of loci

“The method of loci (plural of Latin locus for place or location), also called the memory palace, is a mnemonic device introduced in ancient Roman rhetorical treatises (in the anonymous Rhetorica ad Herennium, Cicero‘s De Oratore, and Quintilian‘s Institutio oratoria). The items can be remembered in mnemonic system are mentally associated with specific physical locations.[1] It relies on memorized spatial relationships to establish, order and recollect memorial content. The term is most often found in specialised works on psychology, neurobiology and memory, though it was used in the same general way at least as early as the first half of the nineteenth century in works on rhetoric, logic and philosophy.[2]…”

http://en.wikipedia.org/wiki/Memory_palace

Person-Action-Object (PAO) System

“The Person-Action-Object System (or “PAO”) is similar to the person-action Dominic System but it adds an object to the images. The images for the numbers can be created through any method, from the Dominic System to the Major System. Some people assign arbitrary images to the numbers without any phonetic conversion. The digits are usually chunked in 2 or 3 digits. A 2-digit PAO system places 6 digits in a locus, and a 3-digit PAO system places 9 digits per locus…”

http://mnemotechnics.org/wiki/Person-Action-Object_%28PAO%29_System