You can fish your way to 300 cooking and make money at the same time. Here's what I did when I was level 40:
First, I got and completed the fishing quest. Then I went to Gadgetzan to get the cooking quest. Like BrianTheFist, I bought my eggs at the Gadgetzan AH. Unlike him, I fished for the clam meat - one of the things you can catch off the pier at Steamwheedle port is clams, and every clam has meat (it seems like on out of 15 or so also has a pearl).
One of the vendors at Steamwheedle port also sells high-order fish recipes - buy them for the next part. Once you have made the omlette and gotten the artisan training, the fun begins.
Go back to Steamwheedle port buy a stack of firewood from the vendor then catch fish of all sorts. When your packs are full, start a bonfire and cook all the fish you caught. Sell the cooked fish to the vendor, and repeat the process until you are at 300 cooking. You'll probably also be at 300 fishing when you're done as well.
Oh, I did mention making money, didn't I? In addition to selling the cooked fish, there are also Firefin Snappers and Stonescale Eels of the coast of Tanaris, and don't forget the pearls from the clams.
Edited, Mon Nov 21 18:13:05 2005 by ohmikeghod