I've been making my own curry powder for a couple of years. It started because the grocery store where I shop doesn't sell my favorite brand. I usually have all the whole spices on hand, which makes it easy to make a batch. I started with a couple of recipes from cookbook and tweaked them a little each time until I came up with one that suits my tastes perfectly.
According to The Spicy Food Lover's Bible, there is a USDA standard for curry powder - 36 % coriander, 28 % turmeric, 10 % cumin, 10 % fenugreek, 4 % white pepper, 3 % allspice, 2 % mustard, 2 % red pepper, and 2 % ginger. If you find that most brands of curry powder available in the U.S. taste the same, it's probably that they're following this standard. I find that these kinds of curry powders are fine in small doses, such as when you're mostly after the color, but the spices aren't very well balanced when you use them in larger amounts. They contain too much turmeric, for one thing, which tends to be bitter. I also find that they don't contain nearly as much cumin as I'd like.
If you're not crazy about most of the curry powders on the market or you if just want to make your own, give this one a try. Then you can tweak later batches for your own taste.
Here are some recipes from this blog using curry powder.
25 cardamom pods
7 teaspoons coriander seeds
4 teaspoons cumin seeds
3 teaspoons black or brown mustard seeds
3 teaspoons fenugreek seeds
1 teaspoon whole black pepper
1 teaspoon whole cloves
1 teaspoon whole fennel
2 teaspoons turmeric
Slice each cardamom pod in half down the middle and shake out the small black seeds. You should end up with about a teaspoon of seeds. Discard the green outer pods.
Heat a skillet to medium. Add the cardamom seeds, coriander, cumin, mustard, fenugreek, peppercorns, cloves, and fennel. Toast the seeds, stirring frequently, until fragrant, about 5 minutes.
Transfer toasted seeds to a spice grinder and grind to a fine powder. Stir in turmeric.
Makes about 1/3 cup.