Apart from the audio:
http://words.bininjgunwok.org.au/words

...the next best thing is probably to just give the IPA here as the usual kind of English transliteration is always so dodgy (writing "boon" will have people thinking it sounds as a ryhme with "soon" which it isn't). If you want to brush up your IPA, the wikipedia vowel chart is excellent. It even has audio.
http://en.wikipedia.org/wiki/IPA_vowel_chart_with_audio

IPA [ˈŋabʊn]

nga- 'first person singular' I
-bun is the verb stem 'to hit/strike' which is also in the present tense. In the past tense, this verb changes to -bom.
nga-bom 'I struck it/him/her'

Here are some other changes:

nga-buni 'I was hitting it' or 'I used to hit it'
nga-buyi 'I might have/should have hit it' and this is also the form when you use the negative in the past tense:
Minj nga-buyi. 'I didn't hit it/him/her' (perhaps teachers might hear this from your students occasionally)
Some speakers say minj nga-buyinj.
The command form (the imperative) drops the final nasal off and is -bu
Yi-bu! Hit it! (addressing one person)

Note this verb -bun is formative in many other verbs that end with -bun such as:
-bidbun 'climb'
-marnbun 'make/fix/create'
-ngeybun 'say the name of'
-bimbun 'paint, write, draw'
-madbun 'wait for'
...and many more

There is also a new meaning of -bun which has developed recently in relation to phones, especially mobile phones. The meaning is 'to dial a number'. To 'make a call' is nga-wokngimen which literally means 'I-speech-go.inside' but the -bun verb is used for dialing the number. Perhaps this is a good candidate for Bininj Kunwok 'word of the year' (in the manner of lexicographers who annually announce new words in their dictionary projects around this time of year— thanks to Chips Mackinolty in Darwin for suggesting this!).

Here's one for the school yard supervisor:
Nangale bi-bom?
Who hit him/her? (when the hitter is male)
Or if you suspect the hitter was female:
Ngalngale bi-bom?
Who hit him/her.

Kabi-bun.
She/he is hitting him/her.

Yimeng "kaluk nga-bun".
He/she said "I am going to hit him/her/it".

Yi-dulkbu!
Strike the tree!

Yun kan-bun!
Don't hit me. (when addressing one person).
Yun kandi-bun! (when addressing more than one).

Yun yiben-bun!
Don't hit them!

Nga-wokngimen, kanwo namba ngah-bun.
I'm going to make a call, give me the number, I'll dial it.