a) Gobs of well-thought out familiars, both mundane and fantastic. Include utilitarian types (monkey, parrot) with cute or theme ones (songbird: +2 perform; bumblebee: +2 intimidate) and suchlike.
b) Feats that give access to dramatically improved familiars. Construct, battle-worthy, elemental, undead, inanimate (see Pet Rock thread), planar (celestial/fiendish), &c &c.
c) Spells that directly affect familiars. Spells that only affect familiars should be more powerful than "normal" spells of that level, because the master is risking a lot by utilizing the familiar instead of himself or another ally. E.g., Polymorph Familiar should be 3rd level, but perhaps last only 10 minutes/level.
d) Most importantly, a whole *bunch* of inspiration on how to use a familiar effectively. Tips, tricks, apt spell combinations, stuff like that. Something to inspire wizards with toad-in-a-bag syndrome.
e) Since there are great paralells between the two, it should also cover psi-stones.