I found a few goodies locally even though I live in urban Chicago. There is gutter spout in the alley behind my building and moss grows where the water flows out. Also, our park and zoo have a pond which has water fern known as Azolla--similar to duck weed. I collected bark from dead trees and vines along a canal or railroad tracks. I do, however, want to buy some quality tropical stuff, like another orchid plant. I found a baby Asian pitcher plant for $10 at a very up-scale garden shop. I very much want that one to succeed! I check Lowes or Home Depot when I'm going by to see what they have in small pots.

Before using anything I've learned to google the plant genus in mind and read up on it. I find out it's temperature and humidity requirements, if it needs a dry period of year or a dormancy period, special requirement (like has to be watered on full moon but not if it's a Tuesday), How big does it grow, the amount of light needed--very important. Fluorescent light is the equivilent to shade usually, unless the plant is one or two inches away from the light. If the plant is not compatible with my ter, I put it in the window.

I also want to try on-line specialty growers but have not gotten around to it.

That's what I've learned. Always learning new things.

The Violet Barn at www.violetbarn.com has small terrarium plants.

doing an internet search for it will give even more results then this:

black jungle, tropiflora, Botanique, cpjungle, cloudjungle

for orchids: Oak Hill, Hoosiers, Andy's, Exotic Orchids of Maui, Santa Barbara Orchid Estates, petite plaisance, J&L orchids, Woodstream, Mountain orchids, and countless others...

Like Client_M said, I like the Violet barn, their quality and great service is fantastic!
Here's a pic of the ones I bought while back, and they were in transit for 14 days (NY to Guam) somehow they 'lost' their way.
The pic shows them as soon as I opened the package.
Black Jungle is also good, but my experience with them is only on 'dry goods' since they don't have phyto certs. for their plants and it's needed for Guam.
Ana :)

Here is a link that might be useful: minuature plants

I second the Rob's recommendation. (or third it. Whatever. . . ) Also, if by bog plants you mean carnivorous ones, check out Cook's.