  Scaling relations of observed galaxy cluster properties are useful tools for
constraining cosmological parameters as well as cluster formation histories.
One of the key cosmological parameters, sigma8, is constrained using observed
clusters of galaxies, although current estimates of sigma8 from the scaling
relations of dynamically relaxed galaxy clusters are limited by the large
scatter in the observed cluster mass-temperature (M-T) relation. With a sample
of eight strong lensing clusters at 0.3 < z <0.8, we find that the observed
cluster concentration-mass relation can be used to reduce the M-T scatter by a
factor of 6. Typically only relaxed clusters are used to estimate sigma8, but
combining the cluster concentration-mass relation with the M-T relation enables
the inclusion of unrelaxed clusters as well. Thus, the resultant gains in the
accuracy of sigma8 measurements from clusters are twofold: the errors on sigma8
are reduced and the cluster sample size is increased. Therefore, the statistics
on sigma8 determination from clusters are greatly improved by the inclusion of
unrelaxed clusters. Exploring cluster scaling relations further, we find that
the correlation between brightest cluster galaxy (BCG) luminosity and cluster
mass offers insight into the assembly histories of clusters. We find
preliminary evidence for a steeper BCG luminosity - cluster mass relation for
strong lensing clusters than the general cluster population, hinting that
strong lensing clusters may have had more active merging histories.
