The Cartel Market is the Old Republics new primary source for the most rare items, unlocks, and gameplay enhancements; but what do you do when you've purchased everything you want and/or don't want to shell out the real cash for an item. Lucky for you anything that can be purchased on the Cartel Market can be sold on the GTN including things like weekly warzone passes and quickbar unlocks. This provides a valuable secondary market where you can make some extra credits or pick up a cartel item without spending any of your hard earned dollars.
Selling an Item
The first thing to know about selling items from the Cartel Market is that when they are first purchased, items will be bound to you for a period of time. If you're a subscriber the timer is shorter and you will be able to sell items after having them in your inventory for 2 days. F2Pers have to wait a little longer and can sell their items after 3 days. You can see the bind time remaining by mousing over the item in your inventory.
Once the bind timer has expired you are free to trade or sell your items through any means you choose, including posting them on the GTN. When you bring up the GTN interface you'll notice that it now has a category specifically for Cartel Items and is broken down even further into he various subcategories of items you'll find on the Cartel Market.
To make a decent amount of credits from Cartel market items there are really only two ways to go as of right now. Selling rare items out of Cartel Packs and consumable items that people require each week, such as warzone and flashpoint passes.
Cartel packs can be a bit of a gamble as the majority of the items are not very rare and the market has already been saturated to the point where there is little to no credits to be made. Only the extremely rare and coveted items like the Nihilus Mask, Holo Statues and Throne Mount bring a healthy dose of credits (Throne Mounts going for 1million credits and up on some servers). Another road some have been taking with the packs is just selling them intact. Why risk getting items only worth 10k when you can leave the chance up to someone else and sell it for 300k. Unless Bioware updates the contents of these packs regularly however, these too will fall in value.
For a more guaranteed bet you can sell the consumable weekly passes for Flashpoints, Operations, and Warzones. With a large population of strictly F2Pers there will always be a market for them, and they currently fetch in the hundreds of thousands of credits each.