1337 (idea)

The thing about l33t is, there's no set alphabet standard. This means that pretty much everybody has their own personal l33t dialect, some more understandable than others. I, for example, when I must stoop to speaking to script kiddies and the like in their own language, tend to intersperse regular English letters, as you can see above. This is mostly because I'm too lazy to make the three keystrokes necessary for '/\/' instead of just one for 'n.' It's also much faster, and unlike script kiddies I actually take the time to spell things properly in l33t. That said: herein follows a transcription of English letters --> l33t characters. j00z d1s w1s3l33, 6r4s5h0pp3r.

A = @, 4, occasionally /\
B = 8, sometimes |3 although this can be confused for 'le'
C = ( (left parenthesis mark), sometimes © (ALT + 0169)
D = |) or |>
E = 3
F = |=
G = 6
H = # or |-|
I = 1 or |
J = J does not seem to have a l33t analog, although it is used in the construction of words such as j00 (you)
K = |<
L = 1 (you can usually tell if it's an L or an I from context), occasionally |_
M = /\/\
N = /\/
O = 0 (zero)
P = |¤ (ALT + 0164), other variations on this theme
Q = I have occasionally seen Q written as 9, although script kiddies are just as likely to use 'kw' for the sound
R = |2 or 2
S = $ or 5
T = 7 or +
U = I usually write 'u' as a capital V
V = \/
W = \/\/ (for clarity \ / \ / )
X = ><
Y = ¥ (ALT + 0165), although as noted above 'J' is frequently used as well
Z = 2 (can usually be spotted from context)