They say that the various species of Sambucus are toxic. They aren't, very.
You'll find the mildly toxic cyanoglycoside sambunigrin in the leaves and unripe fruits of Sambucus species.
The red elderberry (Sambucus racemosa) is the most toxic of the three species, but its toxicity is confined to a tummy ache.
The annual dwarf elder (Sambucus ebulus) is considered completely nontoxic.
The seeds of all Sambucus species contain a resin which is nauseant and diuretic; this resin is destroyed by cooking.
(That's from Buff + v.d.Dunck: Giftpflanzen in Natur und Garten, 1988.)
"It's deadly, it contains cyanide!" say those who don't have a clue. Yeah, right ...
... cyanide is the stuff of detective stories. Cyanoglycosides are found in most if not all rose family plants, and they're the taste behind bitter almonds and amaretto. There's not all that much in elder: the irritation of elder is more due to the resin than the sambunigrin.
The berries of black elder (Sambucus nigra) are made into all sorts of things, as are of course its flowers. It's not wild here, else I'm sure I'd be wild about it. (Blue elder (Sambucus caerulea) and American elder (Sambucus canadensis) are no more; they're subspecies of black elder now.)
I made jam of red elderberries years ago. "Tasty", said those who tried it, and, "Do you have more?". My throat was raw from breathing the fumes while stirring the jam, and the taste (to me) was more of that same raw feeling, so I said, no, I don't have more, nor will I make more, at least for the next few years.
The fruit balls of red elderberry are so tight that they're all moldy inside if you're late in your picking. I've been contemplating making a new batch for the last couple of years, but alas, the berry balls have been over the hill by the time I've remembered to look at the red elderberry bushes.
Making red elderberry jam: Boil the berries with a little water and a bit of sugar, crank through the thingy (1), and bring the now uniform mess to a boil. Seeds will float to the top; pick them off as they do so as they contain most of the whatnots which make raw red elderberry bad for you. Any foam should also be picked off.
(1) I've one of those three-legged hand-cranked apple jam thingies which come with various-size sieves. (I'd love to get the real name for it. Thingy sounds so unprofessional.)
I've seen red elderberry in Oregon as well; their fruit balls were far airier, and I wouldn't expect mold there.
Flowers, leaf and bark of black elder are medicinal; check King's and the rest of them.
Related entry: Elderflower syrup