Triangle-free Lemma Theorem (Triangle-free Lemma). For all $\eta>0$ there exists $c > 0$ and $n_0$ so that every graph $G$ on $n>n_0$ vertices, which contains at most $cn^3$ triangles can be made
triangle free by removing at most $\eta\binom{n}{2}$ edges.
I am trying to find some information related to this topic, I am unable to access the orignal paper by Ruzsa & Szemeredi. 
Does anyone know any useful papers/books on the triangle-free lemma? 
 A: If you're already comfortable with ultrafilters, the new proof of Elek and Szegedy (on the arxiv) derives this (and the more general simplex removal lemma for hypergraphs) from Lebesgue's "points of density" theorem. It's not an easy read, but it is a nice proof.
A: Jacob Fox has just posted A new proof of the graph removal lemma to the arXiv, containing a proof that does not use regularity directly, and thereby accomplishes some more effective bounds.
A: Possibly an even better place to look is in surveys on graph property testing; this is by far the most common use nowadays of the triangle removal lemma, and any sufficiently good introduction to the subject should have some information on it. (I haven't actually read it, but I believe the most recent edition of Alon and Spencer's The Probabilistic Method has a chapter on property testing. If you have access to a copy, assuming the new chapter is anywhere near as good as the rest of the book, that would be my first recommendation.)
If you want a proof and some applications to more traditional combinatorics, Tim Gowers has a wonderful two-paragraph sketch and some discussion here (about halfway down the post).
A: The standard name is 'triangle removal lemma'. Google search gives many results. The original paper of Ruzsa and Szemerédi is not the best reference, as they use an early version of Szemerédi regularity lemma, rather than the more convenient modern version. I recommend reading some surveys on the regularity lemma. A good example is one by Komlós and Simonovits.
A: The recent survey paper 
D. Conlon and J. Fox, Graph removal lemmas, Surveys in Combinatorics, Cambridge University Press, 2013, 1-50 
is on the triangle removal lemma and its various extensions. 
