I'm going with Muskogee (a.k.a. Creek), as it's one of the first NAILs I ever looked into and got resources for. Plus it has a very interesting grammar (from what I've read so far). I've been fiddling with it the past few days.
I'm using the textbook, Beginning Creek: Mvskoke Emponvkv by Innes, Alexander, and Tilkens. Which is a great textbook, though a bit technical.
The first two chapters cover pronunciation. I'm only going over the first chapter for now.
a - like a in father
c - like ch in church
e - like i in pit
́́ē - like i in machine
f - like English f
h - "
i - like ay in bay
k - like English
l - "
m - "
n - "
o - like o in go (pure though, not diphthongized), also like oo in book
p - like English
r - not found in English /ɬ/
s - like English
t - "
u - like oo in book
v - schwa /ə/
w - like English
y - "
These are approximate values, of course.
It should also be noted that under certain circumstances <c>, <k>, <t>, <p>, and <s> can be voiced. This seems to be at the beginning of words, before vowels, and in consonant clusters where the second sound is voiced (much like other NAILs I've studied).
Also note that <v> represents a vowel sound, and <r> represents /ɬ/.
The vowels all have long and short variations, except for <i> which is always long:
Note however, that Muskogee spelling is a bit inconsistent in this regard. Thus <a> is not always the long vowel /aː/ and <v> does not always represent the short vowel /ə/. Also, both <o> and <u> represent the short /o/ sound and <o> represents both the long /o:/ and short /o/ form of that vowel.
The next chapter goes over the tonal accent, that should be interesting. I wasn't even aware that Muskogee had tones.