Is there a summary in Civ5 of all currently active (trade) agreements with all other civs?
I haven't found out yet whether there exists a (trade) agreement overview.
That is, is there some list of all active agreements or do I always have to check per other civ in its agreement history?
There is only the deal history you already found (Diplomacy -> Diplomacy Overview -> Deal history). The history differentiates between active and older deals, so you only have to check the list of active agreements.
Lets hope they provide some better overview with a future patch.