Hoi
The new Monster Summoner Handbook brought the Expanded Summon Monster feat
http://www.d20pfsrd.com/feats/general-feats/expanded-summon-monster
So, 18 new monsters for a summoner, 2 per each summon level.
What to choose?
For 3rd grade I am currently considering Thoqqa for melee and stone tunnel burrowing and the Luyrakien Azata as template for a guardian spirit / general usefulness with many different small and big abilites.
What would you recommend for the other 8 grades? We will be playing in a campaign with a mixture of survival, stealth, guerilla combat and low ressources (for everything). My general idea would be some heavy combat and some utility/SLA monsters.
Thanks!