Sweet alyssum
Datura "Evening fragrance"
White Petunia grandiflora
White Dianthus
Pansy "Crystal clear white"
Osteospermum "Asti white" (it has dark center)
Vinca "Titan white"

mini zinnias
bacopa
tahitian bridal veil - I found conflicting info on google trying to supply latin name, but the one I'm thinking of - foliage looks like tradescantia but smaller, little white flowers that kind of stick out away from the plant.

Thanks for your ideas. Is Diamond Frost like the tahitian bridal veil?

While a few of my favorites have been mentioned, others I would suggest include

Moonflower vine
White penta
White snapdragons
Baby's breath
White marguerite daisy

Definitely White Bacopa! Awesome plant! Also try some White Sweet Alyssum. I'm just trying the Alyssum so can't comment on it yet except to say it's really fragrant for me so far!

Here's a pic of my petunia's last year with the white bacopa:

{{gwi:8477}}

I'm not familiar with diamond frost. {{gwi:8476}} is what's in my mind's eye.

I appreciate all of your suggestions so much...thanks! I do want to include a few white upright geraniums. Can any of you recommend a reliable big bloomer? Thanks again.