You can spend a weekend coming up with peg words for numbers from 0 to 99 in the mnemonic major system and memorizing them. Then you'll have a system for easily memorizing any sequence of up to a 100 arbitrary items by associating the pegs to them, without needing to figure out how to tie the items into each other with rhyming.
Doesn't work in the long term since the associations will fade and you'll re-use the pegs, but long-term stuff can go into a spaced repetition system.
I think memory palaces work reasonably well long-term.
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.