C_a_c_a
c_e_c_e_
s_i_s_i_
s_o_s_o_
s_n_s_n_
b_r_b_r_
a_a_a_a_
a_l_a_l_
Maybe this is cheating, but a quick UNIX command while I eat my lunch here:
egrep -i -e ‘^c.a.c.a$’ -e ‘^c.e.c.e.' -e '^s.i.s.i.’ -e ‘^s.o.s.o.' -e '^s.n.s.n.’ -e ‘^b.r.b.r.' -e '^a.a.a.a.’ -e ‘^a.l.a.l.$’ /usr/dict/words
Turns up answers for 4 of the 8:
beriberi
singsong
snowshoe
swimsuit
Of course it’s cheating! You could look it up in a crossword solver too, but what fun is that? 
Tea gave me the rest:
charcoal
clencher
clenched
clenches
alliable
apadanas
atalayas
amadavat
avadavat
Yes, I know it’s cheating, so we spoilered it.
Harumph. What fun is it when you just consult a database?
I bet you use the auto-solve on sudoku, too. 
Cocoa
Cecil
Sissy
So-so
Snisn
Brrr brrr
Alalalal
Aallaall
Is there a reason the first word is capitalized but the rest aren’t? Because if doesn’t make a difference, then Alabaman fits.
The only reason the first letter is capitalized is the board software doesn’t like posts in all caps.
The only one I see right off…
beriberi
ETA: Make that two – snowshoe
Is it really “C_a_c_a” or is there supposed to be a final missing letter at the end like the others (“C_a_c_a_”)?
Yes, it is supposed to be C_A_C_A_.
Beriberi and snowshoe are correct. At least, I haven’t found any other words that match that pattern.
how about: i–i-i-i-i-i-i-- ?
C_a_c_a
c_e_c_e_ = clenched/clenches?
s_i_s_i_
s_o_s_o_ = singsong
s_n_s_n_
b_r_b_r_ = beriberi?
a_a_a_a_ = Alabaman?
ETA:
Charcoal.
Indivisibility.
Crap, messed up edit in haste - “singsong” is obviously one place too high in the above post.
s_i_s_i_ = slipskin
swimsuit
Almost. Not quite.
Indivisibilities. 
I couldn’t be bothered to count the eyes, they made my i’s go funny :).