A. Aquiel Uhnari
B. Bun, Janeway wore her hair in one.
D. Distress (The crew of the Enterprise was in this state)
E. Exothermic Reaction
F. Faaaaaaaaaaaaaaake!!, it's a
H. Harry Mudd
I. Iotians - from the TOS episode "A Piece of the Action". The Iotians inhabit the planet Sigma Iotia II.
J. J25, System. As featured in "Q Who"
L. Lizard (Charlie X turned that girl into one)
M. Minsharra Class Planet
O. Odan (the Trill on TNG
P. Peter Preston (i should get double score
Q. Quantum Slipstream Drive
S. Samuel Clemens
T. Toroidal antenna
U. USS Enterprise
X. Xhosa (Freighter captained by Kasidy Yates)