I've done several. Roses, lilca, crepe myrtle, nuts and butterfly bushes. There are others but I can't remember their names right now.

I know that Renee's Garden has seeds for Butterfly Bushes and Miniature Roses.

T

Here is a link that might be useful: Renee's Garden

I'm WS hypericum/St. John's wort, spirea, potentilla/cinquefoil, caryopteris/blue mist shrub, apple & pear trees from seed this year. Seeds were harvested from my own shrubs as well as a few neighbors.' Last year I grew Cornus kousa/Kousa dogwood from seed--they grew to 14" tall before going dormant in November. Also grew butterfly bush from seeds received in trade plus rose of Sharon from seeds I harvested from a neighbor's shrub. I have enough excess seeds to send you a trade's worth of most of these if you're interested. Please send me an email or post here.

From what I've read, the dogwoods need an extended cold period but they winter sowed for me last year. I expect the other seeds need some cold as well but I'd Google the propagation information on each to be sure.

Sowing seed it fun and fascinating but just a few words of caution. I am sure you know that if you sow seed of a shrub it will not necessarily produce offspring identical to the parent unless the parent is a species, rather than a hybrid. Secondly if you want to produce new shrubs quickly cuttings and/or layering will make a bigger plant faster than seed. The common things like forsythia, weigela, philadelphus etc all grow easily from cuttings. A 2 foot forsythia cutting can be a 4 foot bush in a year.
Also, 'shrub' covers a huge number of different plants with varying degrees of ease of germination. For example, I have just got some Symplocus paniculata seedling coming up which I sowed in November 2009. So you might need to be patient!

I've winter-sowed New Jersey Tea (Ceanothus americana), Silky Dogwood (Cornus amomum), and Flowering Dogwood (Cornus florida) from seed that I bought or collected with great success. However, I sowed them in late fall or early winter so they had a long cold stratification period. I also sowed Fringe tree last year, and that didn't sprout the first year. It needs 2 years to sprout.

Apparently there are some trees and shrubs that will germinate right away in warm temps, but most require cold and sometimes both warm/cold stratification before germinating. Check out the link below for more specific info.

Here is a link that might be useful: Tom Clothier's Quick reference for tree/shrub germination