Starlight summons, moonlight summons, sunlight summons, nimble summons.
Superior Summons adds on creature every time you summon multiple monsters.
In the super genius beyond bloodlines 3rd party product there was an ability where a sorceror could grant bloodline powers to a summon monster as if it was a sorceror of a level equal to its HD. That opens up a huge variety of ways you could improve your summons.
The sorcerer celestial bloodline gives them some DR.
I think one of the other bloodlines gives them something else.
There was something in one of the DnD 3.0 splat books if you are allowed to use it.
Other then Augment Summoning what other ways are there to improve the effectiveness of summoned creatures via Summon Monster/Nature's Ally,
a friend told me about a way to turn them into the plant type but we cant remember from where.
You are thinking of a forgotten realms 3.5 book, lost empires of faerun.
Summon topiary?
More likely it is Greenbound Summoning, which was incredibly strong, but could only be applied to Summon Nature's Ally. Basically, all your animals became plant type creatures by acquiring the greenbound template, which also give a some SLA, including Wall of Thorns.
If we're talking 3.5 feats, one of the other very good summoning enhancing feats is Rashemi Elemental Summoning which allows you to summon orglashs or thomils instead of air or earth elementals.
Fetchling Shadow Caller, gives shadow template (not sure if you count that as an improvement, but it is different)
Skeleton Summoner, once per day can give a creature the skeletal template
There are also the various animal shaman druid archtypes. These allow you to apply the young, giant, and advanced templates to the appropriately themed animal summons from SNA.
Fetchling Shadow Caller, gives shadow template (not sure if you count that as an improvement, but it is different)
Skeleton Summoner, once per day can give a creature the skeletal template
I played a summoner who did that for a while.
The good: summoning skeletons was awesome. Especially with supieor summons.
The bad: spell focus necromnacy as a prerequiste. Not a great feat.
The ugly: on the surface, the skeleton template looks cool, in reality it actually makes many summons weaker.