Between reading your question and comments, you seem to be looking more for help with learning and implementing lambda calculus than just the specific question you asked here. If so then I am on the same path so I will share some useful info.
The best book I have, which is not to say the best book possible, is Types and Programming Languages (WorldCat) by Benjamin C. Pierce. I know the title doesn't sound anything like lambda calculus but take a look at λ-Calculus extensions: meaning of extension symbols which list many of the lambda calculi that come from the book. There is code for the book in OCaml and F#.
Try searching in CiteSeerX for research papers on lambda calculus to learn more.
The best λ-Calculus evaluator I have found so far is:
Lambda calculus reduction workbench with info here.
Also, I find that you get much better answers for lambda calculus questions related to programming at CS:StackExchange and math related questions at Math:StackExcahnge.
As for programming languages to implement lambda calculus you will probably need to learn a functional language if you haven't; Yes it's a different beast, but the enlightenment on the other side of the mountain is spectacular. Most of the source code I find uses a functional language such as ML or OCaml, and once you learn one, the rest get easier to learn.
To be more specific, here is the source code for the untyped lambda calculus project, here is the input file to an F# variation of YACC which from reading your previous questions seems to be in your world of knowledge, and here is sample input.
Since the grammar is for implementing a REPL, it starts with toplevel, think command prompt, and accepts multiple commands, which in this case are lambda calculus expressions. Since this grammar is used for many calculi it has parts that are place holders in the earlier examples, thus binding here is more of a place holder.
Finally we get to the part you are after
Note LCID is Lower Case Identifier
Term : AppTerm
| LAMBDA LCID DOT Term
| LAMBDA USCORE DOT Term
AppTerm : ATerm
| AppTerm ATerm
/* Atomic terms are ones that never require extra parentheses */
ATerm : LPAREN Term RPAREN
| LCID