Henk Barendregt and Erik Barendsen [2000] Introduction to Lambda Calculus (available online, at our level, perfect)
Raul Rojas [1998] A Tutorial Introduction to the Lambda Calculus (available online, at our level, very clear)
H.P. Barendregt [1984], The Lambda Calculus (A standard reference. Lots of symbols. The work of an expert. Probably a little above our heads (or certainly my head).)
Handbook of Logic in Computer Science (1992), S.Abramsky, D.Gabbay and T.Maibaum (eds.)
Handbook of Theoretical Computer Science (1990), J. van Leuwen (ed.) (see, for example, Barendregt's article).
J.R.Hindley and J.P. Seldin, An Introduction of Combinators and Lambda Calculus (Well worth a read, but the older typeface is a bit off-putting).
G.Huet and D.C.Oppen(1980), Equations and Rewrite Rules A survey
Rinus Plasmeijer and Marko van Eekelen(1993), Functional Programming and Parallel Graph Rewriting
G.E.Revesz, Lambda Calculus, Combinators and Functional Programming (appeals to me, is that an argument? Uses unusual, but sensible, notation for lambda calculus.)
M.R.Sleep, M.J. Plasmeijer and M.C.J.D. van Eekelen(1993),Term Graph Rewriting-- Theory and Practice