We are located in a rather distinct subgroup on the outskirts of the Virgo Cluster, viz. The number of dwarfs close to the Milky Way, the fact that the distant dwarfs are more luminous on average, and the number of members found since the last time I updated this table, all suggest depressing things about how incomplete our surveys may be even around M31. The Local Group is still a dynamically active environment, if we may judge from tidal stripping of M32, the imminent demise of the newly-found Sagittarius dwarf spheroidal from galactic tides, and the material pulled into the Magellanic Stream for the same reason. Numerous similar groups exist nearby - Sculptor, M81, the M101 or CVn cloud, etc. In Virgo we find a much richer aggregation, at the cluster core.
Compact groups pose some special puzzles.
They contain more spirals than expected from the usual morphology-density relation, and have very short predicted lifetimes against merging. Various workers have considered them to be real but young, the dregs of a once-rich population, constantly forming from more diffuse group environments, long filaments seen lengthwise, and fictitious chance alignments. Recent work on Stephan's Quintet has muddied the waters further, implying a crucial role for bound or captured high-velocity members in pumping the group's energy and keeping it from merging. Genuine clusters exhibit a wide range of galaxy population and content, and are luminous enough to be sampled across large distances. Schemes based on these correlate reasonably well with one another.