Kraken is useful in the water. The seasonal spirits (esp. Lions) can also be useful, but they have a tendency to die and be expensive as well
You can add the 1st level beast summons to armies (esp. those w/ high morale). Scorpion Beasts, Wyverns, and Drakes are good for this. Of course, these units effectiveness to cost ratio is bad and they're usefulness quickly peters out in the wake of Vine Ogres. Wights are good too, but I usually summon just a few and then hold off for Legion. I use Vine MEN as a meat shield against cavalry.... Of course, most of the time I skip ALL of the 4th and lower summons except the Vine spells and cast one or more of the Court spells at Level 6 (Troll, Sea Troll, Draconian, Ether Gate...). The Level 6 summons are where you start to get some meaty troops--I save my gems.
In Enchantment, I use Create Revenant to boost research (I prefer Spectres though), Behemoths are very nice, and I will also use Claymen in a pinch (I usually don't clam very heavily). If you have nice longdead (e.g. Jotunheim, C'tis), you can use Reanimation to create a nice little group of more powerful skeletons. Revive King is useful if you only have weak necromancers (or blood mages) to lead undead.
I have been known to use Corpse Man Construction. Yes, I know they suck, but if you use a staff of storms, they're almost to cheap to pass up. Of course the staff is usually more useful on the battlefield, but until opponents start fielding large amounts of flyers, Frankenstein is cheaper than dirt.
Any blood summon is worthwhile, although I usually skip Spine Devils and Bone Fiends and Serpent Fiends. I use Crossbreeding to create patrolling armies for my hunting grounds.