The Small Spice Bag also has a certain chance to drop some other goods, including Old Spice, Baby Spice, and a recipe for a Delicious Chocolate Cake.
The Old Spice, which is a reference to a brand of deodorant, makes you smell nice. The only result of it is a buff which lasts for five minutes and says "Smelling Great!"
So you smell nice, congrats you stinking plate wearer.
The Baby Spice is a fun buff you can apply to a target which shrinks the target by 50%.
It should be noted that the buff only lasts for 30 seconds, so it's not something you can keep on forever. However it can be useful in some situations, especially if you're a Tauren and can't get in some Lake Wintergrasp structures.
A quick fix, granted, but at least it works.
The other special item the bag drops is a Delicious Chocolate Cake recipe. Cake is yummy, and is clearly greater than pie. People will recognize that this is a BC recipe, and was previously a drop from the daily cooking quests offered in Shattrath.
In addition to it being a drop from the current cooking quests in Wrath, it can also now be bought from the cooking supplies vendors in Dalaran for 10 Dalaran Cooking Awards and some gold. This is a good option for those that have had bad luck with the random number generator.
Overall the Small Spice Bag is rather nice right now, yet I have to wonder if Blizzard will eventually add some things to it in the future. Perhaps some Chilled Meat since it's such an important item in the daily quests, or some more random recipes. Only time will tell.
*The other way to get a Northern Spice is to buy it from a vendor for one Dalaran Cooking Award.