Advances in software and hardware have allowed the introduction of high level ab initio methodology into the undergraduate curriculum.  This study will introduce a variety of computational experiments suitable for advanced students working in small teams.  Specifically, isodesmic and homodesmotic reactions will be used to analyze data on the energies of anions, radicals, cations, cycloalkanes, alkenes and alkynes substituted by methyl, silyl, trifluoromethyl, fluoro, cyano, vinyl, and ethynyl.  Each structure in the study can be optimized at the B3LYP/6-31G* level in a few minutes using Spartan '04 running on a commercial Dell computer.  Within each chemical system, the effects of sigma donation (-CH₃ and -SiH₃), sigma withdrawal (-F, -CF₃), pi donation (-NH₂), pi withdrawal (-CN), and conjugation (vinyl, ethynyl) are explored.  Among other things, students can deduce that pi (de)stabilization is (often) larger than sigma, that radicals are stabilized by both donors and acceptors, that sp carbons are more electronegative than sp2 carbons, and that carbons on cyclopropane are "special", not like carbons on alkanes or cycloalkanes.