For ethical reasons, I can't put up what I use in my own practices on a public web site. I would, however, refer you to this:
As Leisha pointed out, Cat's book is a good one.
There's a bunch of other great resources. You can look into our hoodoo group here, or you can look at Lucky Mojo's stuff at www.luckymojo.com (they have an online resource there.)
Hyatt's books are a great resource, but somewhat of a chore to wade through (and to obtain, i believe the complete set would cost you around $4000 on ebay, since they're out of print and the university that retains the copyright has no intent of republishing them.)
There are many, many herbs (and animal curios,) that are used for hexing, crossing, etc, in various different ways. One example would be graveyard dirt from a murderer or known fraud, another would be crushed cayenne peppers.. Many things can be used to do both positive and negative things, and ammonia would be one good example of this.
I don't know how other's would feel about adding Mullein. I know it is a substitution for graveyard dirt and it is listed as an ingredient to hoodoo black arts incense/powder & goofer dust. Although that is from various web sources. I have not worked with Mullein in magikal fashion (for the lack of better words). My primary use is making a herbal infusion for relieving coughs. Otherwise, I await for correction if mullein is not a proper fit in this category.
Blueberries. Not a herb however it is stated to be used for hexing from Encyclopedia of 5,000 Spells by Judika Illes. Which I can somehow see because of it's deep dark color, understanding that some hexing herbs are black/dark such as black mustard seed, peppercorn and poppy seeds, just to name a few.
Let me add that it is not a substitution for graveyard dirt... (Mullein, that is.) Scott Cunningham's works have really spread that around, though he isn't the originator of this falsehood.
From Hoodoo in Theory and Practice, by Cat Yronwood:
Mullein is known as "graveyard torches" or "witch's candles" because it
grows well-spaced in dry, waste ground and if dipped in oil or lard, the
stalks will burn like torches.
BUT MULLEIN IS NOT GRAVEYARD DIRT.
That story was started in the 1940s by suppliers who wanted to make
money but were afraid to violate the laws regarding tampering with
corpses or graveyard desecration, especially in interstate commerce. The
earliest catalogue in my cokllection that mentions mullein as graveyard
dirt dates to World War Two. By the 1960s,, when i was coming up, you
could still buy real graveyard dirt from any small occult store -- but
ALL the mail order houses and the stores that stocked their
mass-produced products -- sold you either talcum powder or powdered
mullein leaves for graveyard dirt.
The commercially-originated lie that "graveyard dirt" is somehow an old
witchcraft code term for mullein was later picked up and carried as an
urban myth extensively in the white Anglo-Saxon neo=pagan community. It
actually forms part of the myth of the "burning times" in that it
perpetuates the hostorically discredited notion that witches must speak
in code or rish death. (But if you are trying to avoid being burned at
the stake, why use something ILLEGAL like graveyard dirt as code for
something innocuous like mullein leaf???) This myth of a witchy "code"
is still perpetuated through the books of well-meaning but ignorant
people and it is just ... well, not true.
From similar resources it looks like Mullein could be a good scent for enemy work etc:
Mullein (verbascum thapsus -- figwort family)
banish; courage; call evil spirits (incense); hexing with
graveyard dirt; black magic (incense); love, prot; black
magic (incense); prot vs
magic and evil spirits
From the perspective of both folkloric magic and witchcraft, Alchemy Works is probably one of the best sites for your wortcunning needs. It has a wide variety of otherwise tough-to-find herbs used for a variety of purposes in witchcraft.
Botanical.com is also a fantastic resource, including providing a vast body of lore for free on the site.
And I would echo those who suggest cat yronwode's book, and Lucky Mojo in general.
For me, though, the hands-down best source for green magic and witchcraft's wortcunning is the writing of Andrew Chumbley of the Cultus Sabbati, and his Ars Philtron and Viridarium Umbris.
Nice discussion topic Ralakk, I’d like to throw a nice hawthorn thorn into the ring please.
In the UK a lot of witch bottles have been found in old buildings. These are used to bless/protect a place. I have used these in virtually all the homes I have had and have been asked to make them for other people and have taught others to make them too.
In the Museum of Witchcraft in Cornwall (well worth a visit if you are in the UK) they have a few examples of these bottles that have been found in old buildings and donated to the museum. The ones on display have Nails and urine in a bottle, a lambs heart pierced with pins in a glass jar etc. And a common one of those found is something or other pierced with hawthorn thorns.
Hawthorn in the UK has a few common names, Whitethorn, Maywitch and May (May is the month that the May tree blossoms). It is generally considered an unlucky tree and the Irish Gallic name for it means “harm”.
In many folk cultures it is believed that May is a bad/unlucky month for marriages.
The Hawthorn blossom, for many men, has the strong scent of female sexuality and was used by the Turks as an erotic symbol.
In a practical sense it is often planted as a barrier, the thorns can keep out any random trespasser, I have planted some Blackthorn (Sloe) in my garden for that reason (and so I can make sloe gin!!).
Hawthorn is often used in folk spells for purification cleansing and to enhance male potency. Due to the purification use I have made witch bottles with items inside to attract negative influences and added holly to trap them and hawthorn to purify them.
I suppose using the same theory it would be possible to attract luck into the bottle, or to draw harmony into there and then kill it. Purification can be used for both “good” and “bad” reasons. Salt purifies and cleans, but if you put too much of it in the soil it kills it, clean and sterile is not always good, so the same goes for hawthorn.