Inscription spells and abilities
Inscription is an entirely new tradeskill that's being added to the game with Wrath of the Lich King. It's a profession surrounded around enhancing spells and combat abilities, with a side ability to produce buffing scrolls. They're also able to create some trinkets, along with utility scrolls like one that allows you to recall to your hearthstone location. They produce runes and glyphs to change the cosmetic appearance of spells while also changing the effects. Many of the buffs to the spells are equivalent to a full set of talents applying to a single ability - making inscription very valuable for anyone interested in improving their character. They can also produce runewords, which are small buffs that can be applied temporarily to armor and weapons.
It's likely that there will be a rush to the profession when the expansion hits, so you'll likely be able to see what the profession can bring to the table almost immediately after release. Herbalism feeds directly into inscription, creating the reagents for most of the magical inks that you'll need to produce your goods. Players with inscription take stacks of five herbs and mill them into various components. If you're looking to get in with the rush to the profession, it's a good idea to start stockpiling herbs now before everyone else is.
The Wrath of the Lich King beta is still ongoing, so not everything is yet known about the profession. It's still a work in progress, but there's already been some significant work put into the profession. For example, an inscriber can create a Glyph of the Red Lynx, which makes it so that when the druid goes into cat form they appear as a red cat rather than the ordinary panther. It's not all fluff, either - a Glyph of Judgement makes it so that the paladin's judgement spells do 10% more damage. Glyph of Lightwell makes it so that the priest's lightwell spell heals for 20% more. You can see just how powerful this profession really is - when combined with better gear, those percentage improvements will make players far more powerful than they are now.
Some of the glyphs have other additional abilities, like increasing durations, reducing mana costs and other things. It's likely that players will be able to improve their glyphs as inscribers get new recipes, likely with additional, more complex effects. It's exciting to watch this profession develop, and it'll change the way that professions interact with the rest of the game.