What I need are some identities envolving several
boolean variables with the operations of XOR and AND.

Notation: !A represents (not a)
and AB represents (and a b)
and !AB represents (and (not a) b)
and + represents XOR -- A + B <=> (xor a b)

I have the following three identies and have generalized them
to several variables.

t = A + !A
t = A + !AB + !A!B
t = AB + !AB + A!B + !A!B

Are there other identies envolving XOR and AND and NOT?
All others that i can think of are derivable from these
three.

For example:   AB => A   ( => implies)
is equivalent to : t = !(AB) + A + A!(AB)
which apparently simplifies to:  t = A + !AB + !A!B

I'll be very happy to share the lisp code with anyone interested.

Strictly speaking you are not working with 'Boolean algebra' but rather
the algebra of propositions, which is a Boolean algebra. Boolean
algebras categorize a class of mathematical systems including, for
example, the algebra of sets (union, intersection, ...).

Notations vary, but typically when AB is used to represent conjunction
(logical AND) the symbol + is used for disjunction (logical OR, i.e.,
inclusive OR not XOR). Usually, XOR is denoted using a modification of
the symbol for OR, such as the plus/minus sign (a line under the +).
Java uses ^ for its bitwise XOR operator, but this symbol is also
frequently used to represent AND (with v used for OR).

Are you familiar with the use of truth tables? What about DeMorgan's
Laws (+ is OR here):
!(A+B) == !A!B
!(AB) == !A + !B

I would suggest reading a book on elementary mathematical logic to
explore some of the identities you're looking for. In particular, are
you familiar with the idea that all of these operations can be expressed
simply using NOT and AND, i.e., NAND:
AB = !(!(AB)!(AB))
A+B = !(!(AA)!(BB))

In other words,
(defun logical-and (a b) (nand (nand a b) (nand a b)))
(defun logical-or (a b) (nand (nand a a) (nand b b)))

| Does anyone know a lot about boolean algebra?

No.  There isn't a whole lot to know about it.

| What I need are some identities envolving several
| boolean variables with the operations of XOR and AND.
|
| Notation: !A represents (not a)
| and AB represents (and a b)
| and !AB represents (and (not a) b)
| and + represents XOR -- A + B <=> (xor a b)

Calculating with truth values using these operations is equivalent to
doing arithmetic modulo 2, where + corresponds to _xor_, and
multiplication corresponds to _and_.  And finally, negation (not a)
corresponds to adding 1.

In particular, all the standard rules of arithmetic apply.

In fact, one often talks about boolean rings to be rings with identity
in which every element satisfies xx=x:

  http://en.wikipedia.org/wiki/Boolean_ring

There are other ways to axiomatize propositional logic:

  http://en.wikipedia.org/wiki/Propositional_logic

The equational theory ("arithmetic") of BAs is not that exciting,
for sure. But see http://www-unix.mcs.anl.gov/~mccune/papers/robbins/
where a (computer aided) solution to a 60 years old problem is
reported.  

     t = AB + !AB + A!B + !A!B

so special and not, for example:

T = (NOT (XOR
          (NOT
           (AND (XOR (NOT A) T)
                (NOT (XOR (NOT A) (XOR (AND B T) (NOT B))))))
          (NOT (AND C (NOT (XOR (NOT C) T))))))

(and an infinity of other tautologies)?

An example: write down a random boolean polynomial equation like
ABC + BCD + CDE + DEA + EAB + ABDE + CD = false
and try to solve it without just grinding out the truth table.  Now do
the same for
ABC + BCD + 17*CDE + DEA + 3*EAB + ABDE + 5*CD = 0
over the integers, looking for integer solutions.  They're the same
kind of beast, though the latter is harder.