Making money since the start of Cata has been really easy, but I've noticed now things are starting to slow down.
The first 3 days of Cata I spent mining (got two full level ups just from that), while doing that I leveled by BS and was one of the first on the server with some of the 316-333 weapons and plate items which made me a fair amount. Also sold Elem/Pyrite for over the top prices.
Then sat at the AH for the next couple of days and just bought and resold almost any 325+ blue that hit the AH (assuming it wasn't already over priced

) Also picked up 2 BoE Epics while grinding cloth for my girlfriend so that was about 60k right there.
In total I'd say I've made close to 400k since the start of Cata and I've spent about 150k leveling profs and gearing my girlfriend and myself up (her Christmas present was a Vial of the Sands

)
As for making cash now, well people are mostly geared and normal dungeons (and HC's to a lesser extent) are easier to complete with PuG's so hopping on the gear bandwagon won't work very well (depending on your server though, eg. if you're one of 5 people in total making BS epics then maybe there's still cash to be made)
Farming is always constant income but definitely not the smartest use of time right now, rather buy mats and make consumables (Flasks are selling really well right now, certain enchants, new BS belt buckle, etc)
Me personally, I sit at the AH after doing my daily HC and whatever dailies I'm in the mood for and wait for Auctioneer to tell me to buy something
Also check out
The Consortium for tons of gold making information.
PS. if you have a character with enchanting and alchemy you're sorted, make 359 epic alch stone, DE it, profit
