The two languages to which gematria is most frequently applied are 
Hebrew and Greek.

The letter-values of the Hebrew Alphabet (transliterated in the manner 
of the Hermetic Order of the Golden Dawn):

Aleph (ALP)   A    1
Beth (BITh)   B    2
Gimel (GML)   G    3
Daleth (DLTh) D    4
He (HH)       H    5
Vau (VV)      V    6
Zain (ZIN)    Z    7
Cheth (ChITh) Ch   8
Teth (TITh)   T    9
Yod (IVD)     I   10
Kaph (KP)     K   20 (final value: 500)
Lamed (LMD)   L   30
Mem (MIM)     M   40 (final value: 600)
Nun (NVN)     N   50 (final value: 700)
Samekh (SMK)  S   60
Ayin (OIN)    O   70
Pe (PH)       P   80 (final value: 800)
Tzaddi (TzDI) Tz  90 (final value: 900)
Qoph (QVP)    Q  100
Resh (RISh)   R  200
Shin (ShIN)   Sh 300
Tau (ThV)     Th 400

(Note: "final" values may optionally be used if the letter is at 
the end of a word.)

The letter-values of the Greek Alphabet:

Alpha (ALPhA)       A    1
Beta (BHTA)         B    2
Gamma (GAMMA)       G    3
Delta (DELTA)       D    4
Epsilon (EPsILON)   E    5
Zeta (ZHTA)         Z    7
Eta (HTA)           H    8
Theta (ThHTA)       Th   9
Iota (IWTA)         I   10
Kappa (KAPPA)       K   20
Lambda (LAMBDA)     L   30
Mu (MU)             M   40
Nu (NU)             N   50
Xi (XI)             X   60
Omicron (OMIKRON)   O   70
Pi (PI)             P   80
Rho (RW)            R  100
Sigma (SIGMA)       S  200
Tau (TAU)           T  300
Upsilon (UPsILON)   U  400
Phi (PhI)           Ph 500
Chi (ChI)           Ch 600
Psi (PsI)           Ps 700
Omega (WMEGA)       W  800

(Note: the "missing" values of 6 and 90 are taken, respectively, 
by the obsolete letters Digamma (F) and Koppa (Q).)