PrCs for summoning-focussed Spirit Shamans

[CardCaptor]

I've been looking into the Spirit Shaman for a long while now, and found it to look appetizing. It's a class I wouldn't mind taking 20 levels in, except for perhaps the last level of it, but I wonder if I could maybe get more of the class as a whole. I've recently built one for a game I'm in, and I've turned it into a conjurer of sorts, mostly focussing on summoning creatures to assist her. Now, my DM doesn't allow dipping, and in fact, doesn't allow multiclassing, unless it is to meet a prerequirement, and if we are to take a prestige class, we must take all levels of it. I was thinking of dropping out after 11th level to get the cool Ressurection-like ability (especially since it's a no-ressurection game and the DM said this was fine), but I don't seem to see all that many interesting PrCs for these guys. Could I maybe have some suggesttions?

[Umbranar]

I have played a summoning-focussed Spirit Shaman and I had the same issue. I had taken a look at the Thaurmagist(?) of the DMG but decided to go straight spirit shaman up to level 15 when the campaign ended. Rapid Summoning is key imo. I often cast the summon in one round to summon (dire) animals and then Animal Growth. Giant crocodiles with Animal Growth are Garguantian grapple machines.

I guess any class with full caster progression will do but won`t boost your summons directly.

[eggs]

Skypledged from Races of the Wild for Cleric spell access (and/or expanded Druid spell access), including the Summon Monsters, would be my first choice.

[Urpriest]

Moonspeaker (Races of Eberron) is pretty cool for a character focused on SNA, provided you're able to go Shifter.

Edit: I also like Winterhaunt of Iborighu, but it's got a somewhat different focus from what you're going for.