Violets, freesia, pink jasmine and Gregg sage (salvia greggii), especially together in the case of the last two. All of these are perennial or at least come back year after year, though of course violet and freesia die back to the ground, and the jasmine and sage are in bloom much of the year.
I can't say if you could grow any or all of them in your backyard without knowing your climate. All of them do fine in the Mediterranean climate of northern California.
Another deliciously scented plant is angel's trumpet (brugmansia), but two caveats accompany that recommendation: it's highly toxic if ingested, so don't plant it where the incautious will happen across it; and although it smells utterly heavenly, it only does so at night. Plant it outside an open bedroom window and you will dream of heaven.