What do we know about the Black Speech of Mordor?

Question

We know the Ring Verse (Ash Nazg . . .), and single words like 'Ghâsh' (Fire). Do we know any more about canonical Black Speech?

Answer 1

According to Tolkien himself:

The Black Speech was not intentionally modeled on any style, but was meant to be self consistent, very different from Elvish, yet organized and expressive, as would be expected of a device of Sauron before his complete corruption. It was evidently an agglutinative language. [...] I have tried to play fair linguistically, and it is meant to have a meaning not be a mere casual group of nasty noises

"Words, Phrases and Passages in Various Tongues in The Lord of the Rings", Parma Eldalemberon 17, p. 11-12.

This is from an issue of a magazine which contained a collection of notes about the uses of his various invented languages as they occurred in The Lord of the Rings. According to the editor:

Although Tolkien never completed the commentary as originally planned, he retained the more cursory list of words and names from which he was working; and he continued to compose further notes on the grammar and history of the Elvish words and names in the story. Many of these were placed together with "Words, Phrases and Passages," and the main commentary has been supplemented by these notes in this edition. Together these texts give the clearest picture we have of how Tolkien conceived of his linguistic inventions in the forms they were revealed to his readers.

So it's a lot more than just a single verse and some words, but a lot less than a complete language with fully-formed grammar and vocabulary.

Answer 2

Not a lot

We have in total about 32 known words in Tolkien's Black Speech. The majority are from The Lord of the Rings, both from the ring verse you cited, and also in the orcish curse in the Two Towers.

'Lie quiet, or I'll tickle you with this,' he hissed. 'Don't draw attention to yourself, or I may forget my orders. Curse the Isengarders! Uglúk u bagronk sha pushdug Saruman-glob búbhosh skai': he passed into a long angry speech in his own tongue that slowly died away into muttering and snarling.
_{The Lord of the Rings - Book III - Chapter 3 - "The Uruk-Hai"}

In addition, some other sources that have come to light later:

• Parma Eldabaron 17 contains an analysis of the ring inscription, written by JRR Tolkien, a letter Tolkien wrote in 1964 where he talks a bit about Black Speech and gives some example of its verb system, and various glosses Tolkien gave on the handful of Black Speech words found in LotR.
• There's a handful of glosses of some other Black Speech words published in The History of Middle-earth, Unfinished Tales, and Letters of JRR Tolkien.

All together the corpus is still very small and there is not a lot known.

Some resources you may find helpful:

• Eldamo's database on Black Speech
• Analysis by Un4givenOrc (Note that while this website is devoted to a fan extension of the language, this page itself confines itself to just canonical Black Speech and is the best I've seen.)
• Analysis by Helge Fauskanger (Good, but written prior to the publication of PE#17, and so not up to date.)