4 New Prestige Classes:
Dragonchylde (gain dragon powers, then morph into a true dragon--if you can convince a female dragon to eat your corpse, she becomes pregnant with an egg containig your spirit which hatches you as a dragon of her type, lol)
Force Mage (force effects mastery)
Soulbinder (summoning/calling mastery)
Spirit Caller (summons spirits from the spirit world to aid you)
13 New Calling Diagrams that bolster or hamper the abilities of summoned (called) creatures, like adding a symbol of pain effect once per hour on the creature called until it does your bidding, or beefing up the save DCs of its spell-like and supernatural abilities by +2.
35 new conjuration spells, including Bind Guardian I-IX that let you permanently bind summoned monsters to serve you, plus new power word spells.
16 new feats, most specifically for conjurers, but some useful to any class, like Silver Tongue, which makes Bluff, DSiplomacy and Intimidate class skills for you always. Conjurer only type feats include Called Companion, which lets a wizard learn the clerical planar ally spells and lets the wizard's planar allies gain XP and advance.
New magic items like the Bracelet of Foe Charms (works like Bracelet of Friends, except you can turn people into charms and then use the charm to "summon" them to fight for you just as if they were summoned monsters! 'Courswe, after that, they're free to do what they want, which very likely will be to kill you for imprisoning and enslaving them).
Useful tips on how to play a conjurer or defeat them round out the book.
Conjuration, along with Enchantment and Constructs, are my favorites in the Encyclopaedia Arcane series for their ease of use and integration into a game without necessitating variant magic systems. Highly recommended.