I don't know about the other things, but most lemon grass that I've encountered in oriental cooking has been about as big around as a medium sized asparagus.

Turmeric root is generally sold fresh in the few markets that carry it. Most often, it is sold in dry, powder form. It is mostly used as a coloring agent, not for flavor. It colors things a bright yellow, and is the reason some curries are that color. Since it doesn't really impart much flavor, you could use the dry without worrying too much about quantities. A little goes a long way, if a recipe calls for an inch piece of root, I would start with an eighth to quarter tspn and go from there.

A warning note...the yellow dye is quite strong, and can stain anything from rubber spatulas to hands to counters. Be careful with it. Yes, most things can be bleached clean, but some things take some time to lose the color. The rubber bands surrounding orthodontic braces will turn bright green, and it doesn't wear off.

Candlenuts are an oily nut used in Indonesian foods, and are difficult to find. You can substitute macadamia nuts (a close substitute) or Brazil nuts, which are three times as big, so adjust amounts accordingly. You can also use raw cashews or almonds...I'd use about 2 cashews per candlenut called for.

Dried shrimp paste is available in most Asian markets. It's quite strong and smells it. I can't really think of a substitute, but I suppose if I was really stuck, I'd try soaking dried shrimp, and then making a puree with it using enough soy sauce to get the puree going. Don't be put off by the smell, it won't make the dish taste/smell like that if you use the amount called for.

Lemon grass is generally about as long as celery, and most recipes call for just the white part, which is usually about the bottom third of the whole stalk. Don't worry about the waste, because the rest of the stalk can be used to simmer a nice lemony flavor into soups or teas and then removed. Some dishes will call for large pieces to be simmered and then removed, you can use the green part of the stalk for that as well.

The dried lemongrass you can sometimes find is so inferior that you'd be better off substituting lemon or lime juice (I have used a combo of both to best effect)as it is really fit for nothing except brewing into tea. You can freeze lemon grass, so if you find an Asian market that carries it (or decide to plant some of your own) that is a help.

You can buy most of these things in an Indian market -- do you have one nearby?

Thanks everyone. Egganddart - I live in a big metro area so I'm sure we have an Indian market also - I'll check on that. I have President's Day off tomorrow so great day to go off on a hunt to find this stuff.