I make gold selling pots on the AH, but I had to make a couple herb-collecting alts to ease the farming pain.  Although most have been hit-and-miss, healing and switftness pots are consistent sellers.  I started by selling stacks of Healing Potion for 30s, moved onto Greater Healing for 1.80 and now sell Superior for 2.5 (I keep the Major for me and my friends). Swiftness are consistent sellers, but I need my alts to collect the Swiftthistle and Briarthorn.  Outside of those I sell 1-2 mini-stacks of Elixir of Greater Agility and Intellect per week (6g for 5).  Pots that fetch a good price but are hard to sell include Elixir of Shadow Power and Elixir of Superior D.  I've had mixed success with others but specifically I recommend staying away from Dreamless Sleep, Nature Protection (can't give these away), Invisibility and Rage(the prices don't justify the gathering hardships). (I'm a 57th Tauren hunter on Madoran).  In a good week I can sell 4 stacks of Switftness, 4 of Healing, and 2 mini stacks of Agility, and maybe a stack of Wildvine for a total of 35g. Not mind-blowing but it gets me my mount and some nice scopes.

I recommend always setting a starting price you can live with, and a buyout price you think is reasonable.  Swiftness, for whatever reason, sells best during the week, and healing on the weekends.  I find Fridays the prime selling day, so set those auctions up on Thursday night and you'll be set for the weekend.