Hi there
Well, it really depends on what kind of a gardener you are...there are SO many websites out there that can offer you so many different types of plants. One of the sites that I turn to often for new, as well as well established, varieties is White Flower Farm ( easy to find online, can't post link...sorry ). Their catalog, if you request to receive it, is second to none! If you want to start from seed, of course you might want to turn to Burpee Seed Company ( can't post link...sorry ) who offer a truly wide variety of specailty seeds this is, of course, only the "tip of the iceberg" but I hope it's a good place to start having a look around! Hope you find what you're looking for!
Green
I was very pleased with Van Engelen. I ordered 500 fall bulbs for the elementary school. Their site was user friendly and their phone service was extremly helpful. The bulbs were plentiful and healthy.