We report the linear optical absorption spectra of aluminum clusters Aln (n = 2-5) involving valence transitions, computed using the large-scale all-electron configuration interaction (CI) methodology. When compared to the available experimental data for the isomers of Al2 and Al3, our results are in very good agreement as far as important peak positions are concerned. The contribution of configurations to many body wave functions of various excited states suggests that in most cases optical excitations involved are collective, and plasmonic in nature.