Thanks for the guide, this is great. Here is something I tried (and it worked) to level speech to 100 in 10 minutes for 1 gold (PS3, not tested on XBOX360).
1. Use the Fortify Restoration glitch to create a potion over 1,000,000%. Use it to create (2) fortify enchanting potions (mine are about 1,700,000% each).
2. Go to an Enchanting Table with (1) ring of any type and use one of your newly crafted Super Fortify Enchanting potions to create a Super Smithing Ring (if you can add two enchantments, do an alchemy enchantment here too... Good ring to have around, so you don't need to do the fortify enchanting loop every time).
3. Go to a forge and create some armor, something badass, like Daedric Armor. Put on the ring created in step 2 and improve that bad boy at a workbench as much as you can.
4. Go back to the Enchanting Table and suck down that last Fortify Enchanting potion. With a Black or Grand Soul Gem, add a Fortify Sneak enchantment to the armor created in step 3. If your enchanting is high enough, the sneak boost enchanted on the armor should have a negative value, and the armor's value should now also be negative (this is important).
5. Go to any vendor. SAVE THE GAME (just in case). The vendor I used was Enthir at the College of Winterhold (in the Hall of Attainment).
6. Crouch, wait until hidden, and "pickpocket" the armor into the merchant's inventory (you will see that the skill required is "0% to steal/place").
7. Buy the armor from the vendor. Because the value of the item is floored at zero during transactions, you should only pay 1 gold for it, but your speech skill should jump to 100.
Boom, 100 Speech. Go Legendary and repeat with ease. If you repeat, be sure to reequip the armor, if you used it to sneak during step 6 before placing it in the merchant's inventory. Not patched as of this post.