First of all, I want to say that this is a pretty old method but I recently used it again as I am leveling a new character on a new server and I couldn't pay for my flying mount when I hit 60. Secondly, I did not discover this method but I didn't find any posts on it so I thought I would share.
THIS METHOD IS SERVER DEPENDENT, BASED OFF HOW MUCH SMALL RADIANT SHARDS SELL FOR.
So what you do is farm Razorfen Downs. You're going to be running through the instance (you can dodge all trash once you get used to it) and just soloing the bosses for the rare drops. All the rare drops in the instance yield a Small Radiant Shard when disenchanted. You can obtain a minimum of 3 shards per run and a maximum of 5 (Amnennar the Coldbringer sometimes drops 2 blues and there is a rare spawn boss). On my server Small Radiant Shards sell for 15g/each, and mine sold pretty quickly.
I've only tried this with ranged/caster classes, but you should be able to run this 5 times within a hour no matter what level you are (unless you pull lots of trash while you're still learning) so 3x5 = 15 shards minimum for a hour, 15g x 15shards = 225g/hour. I recommend doing some of the Hellfire Peninsula quests so you get some decent gear before trying to do this with Pre-BC greens.
Here is a video showing you how to run through the instance while aggroing almost none of the trash. This video was not made by me.
[ame=http://www.youtube.com/watch?v=W4NApYsUe00]YouTube - Napalm - Solo RFD in 5 minutes ( wow gold farm )[/ame]
Thanks for reading, and sorry if it's a repost. Link an original and I'll take this down.