On a whim I decided to level my alt into Enchanting. I make so much money prospecting ore and cutting gems that there's no need to mine anymore. And Enchanting seems like a lot more fun since Vellum allows enchants to be sold and mailed.
There's a zillion enchanting powerlevelling guides out there that'll tell you what recipes to make on the way up. I found this guide most useful. It's mostly correct although it recommends some awkward patterns around 290 and after 325. The nice thing is it has you levelling up on Outands mats as much as possible through 375. You can switch to Northrend mats at 350, but those are so expensive now you're better off sticking with the old recipes if you can find ones you'll get skill points from.
I simply bought all the mats at the auction house, about 2500g total to get me to 375. The only stuff that was hard to come by was Dream Dust and Greater Planar Essence, both of those were in short supply. In general you'll be levelling up entirely on dust and essence; you don't really need to use shards to level up. You may choose to though, particularly 300-375 where shards are much cheaper than essences.
From 0-375 you're making garbage no one wants, so be prepared to spend a lot of gold and throw out the results. After 375 you can skill up entirely by making enchants on vellum, then selling the enchanting scrolls. At least on my realm this market is still open and people seem to be buying. Nice way to make your money back.
I found it easiest to stay in Darnassus until I was at skill 300. In theory you should make a side trip to Moonglade around 275 to pick up a couple of things but I was able to skip it by buying the rod recipe on the AH. At 300 you need to head to the Outlands: Shattrath if you're Scryer, Aldor to Hellfire Peninsula. Stay there until you decide to switch to Northrend enchants (at 350-375). You have to visit a vendor in Shattrath once or twice and I ended up going to Caverns of Time for the ring enchant to get me up towards 370.
It's tedious getting 375 skill points. Took me about three hours. The following macro helped a bit: with it you can get it down to clicking the enchant button in the tradeskill window, then pressing a hotkey for the macro to automatically apply the enchant to your top left bag slot item. There's probably a way to automate the enchant button in the macro too but 3.0 changed the APIs so the old scripts don't work.
/click ContainerFrame0Item1/script ReplaceEnchant();
I'm optimistic that enchanting will be profitable in WotLK. Vellum means you can sell enchants conveniently. And the new crafting system means even seldom played alts can quickly get all the patterns; no rare BoP drops. It's a wide open market.
Special request to all readers: do not vendor BoE greens. Please, post them on the AH for 10g, or give them to an enchanter friend, or something. Everyone else vendored the green crap they got levelling up, just like me, and it turns out that the enchanting market is full of shards (from blues) but very little dust or essence (from greens).