There are a bunch of plants called alyssum, the one you're talking about is probably sweet alyssum, aka lobularia maritima. I find it's usually honey-scented, especially in sunshine, but some more so than others, and it's hard to tell if it's the seed source, the growing conditions, or maybe the influence of little plant elves! You could try from seed, but I doubt there are specific varieties for fragrance, it's such a common annual, the only way to be sure is to visit a few nurseries and sniff 'em for yourself.

Jim

I'm willing to bet your neighbor is sprinkling seeds in early spring or the plants are self-sowing. Is it used as an edger? The white ones seem to be the most fragrant. They are one of the wonderful plants that seem to thrive on neglect. It seems a little early for them, but it is much colder here, esp. this spring.

They're growing in the sun, and are all white. I guess they're self seeding. It's a large mat in a small bed, like a groundcover. Not in bloom yet really, but I notice it a lot later in the summer. I was at the nursery today, and it seems the white ones are the ones that smell. Unlike petunias, where the purple ones are the only smelly ones! I wonder if alyssum can overwinter? I seem to have zero luck with alyssum, but I'm going to try again. I can't understand it, they should be so hardy!
Thanks for the help!