Well there is an enchanting recipe that turns 3 small prismatic shards into a large one.
It is:
Large Prismatic Shard - Spells - World of Warcraft
You can buy the recipe from the enchanting vendor in Lower City.
You need 335 enchanting to learn this. With it you can make about 5g every 5 seconds. Because thats how long it takes to cast it
Small Prismatic Shards usually go for around 5g each. Large Prismatic Shards usually go for around 20-22g each. So, just buy out all of the small Prismatic Shards. And turn them into large ones, you will make about 5g profit off of every three shards.
This isnt a great way to make money FAST, but hey, if your lazy like me and just sit in IF cuz your bored, then why not buyout the AH and make about 100g, instead of just sitting there.
Hope this helps some people make easy cash!