Has anyone had much luck setting up and supplying to raiders that can't wait to upgrade?
It's a method that requires having a large stock of materials, but I find it can be very profitable. Some weeknights I set up shop outside Ulduar or previously Naxxramas with a bag full of spell threads, leg armours, cut gems, flasks and food. This is a trick that works best for an enchanter, as stocking enchant scrolls as opposed to just basic materials can get really expensive and is a much riskier prospect as we have no idea what enchants might sell.
Over the course of the raid night, I send out notes in general about every 2-5 minutes, wooing raiders who just got spiffy new gear to come and get it enhanced right now so they can continue to raid with their new gear without having to take the time to go back to civilization and get it done, as well as providing consumables for people who forgot to shop or didn't buy enough.
When selling in this method, I price my stuff between 5-10% higher than I could get for it on the AH as a convenience tag. This has slowed down somewhat since Ulduar came out, but as more people manage to break through on this content, the better sales get. The downside is you have to know your raiding market very well, or you'll be stocking items that will never sell.
I usually have the following in my bags at the start of the night, and some nights I have to retire early as I sell out;
10-15 each Flask of the Frost Wyrm, Flask of Endless Rage
5-10 Flask of Pure Mojo, Flask of Stoneblood
40 Runic Mana Potion
40 Runic Healing Potion
3 each, Runed, Bold and Delicate Scarlet Rubies, Smooth and Rigid Autumn’s Glow, Solid and Sparkling Sky Sapphires.
2 each, Veiled and Glinting Monarch Topaz, Soverign and Royal Twilight Opals, Jagged Forest Emeralds
20 each; Worg Tartare, Snapper Extreme (hit food), Poached Northern Sculpin (+AP), Spicy Fried Herring (+mp5), Firecracker Salmon (+dps), Blackened Dragonfin (+agi)
I try and do this regularly on Wednesday nights (having hit every guild website I could find for my server to check out their raid times

) and it’s gotten to the point where I have regular customers, and some raid leaders sending underprepared people out the doors to do some last minute shopping. I make an effort not to be irritating about it (no spamming my services, ignoring jerks etc) and some would be comedians will try and sharpen their teeth on you in general no matter how professional a front you put up, but it’s worth it when the next week they’re coming buy to get a spellthread for the new pants as the raid leader won’t wait for them to go to town for it.
Everyone’s server is different, experiment and see what sells well at the doors to hell on yours!