Since EECP has an old version of ECP (As does Y2K3), I switched to the improved DMA Army Pack which is compatible with the latest ECP. I've also got some other mods that change the setting, such as SEBNAMII for Vietnam, Liberation 41-45 and Invasion 44 for WW2 action. I also grabbed Swedish Forces Pack 4. Whenever possible I use them with ECP to help improve the gameplay.
Missionwise, I like the dynamic missions and templates from DMA Group and have added their anims, especially leaning, to all my mod's configs. For campaigns, I've got 1969 Vietnam (SEBNAMII), Blue Storm (FDFMod), Blue Sky, Insurgency, PMC Fury, PMC Heroes, PMC Rangers, Retaliation, Revolt 1988, Revolution 1983, Talvisto, and Delta Ops 1. I've got a lot more SP missions too for each mod. More than enough gaming to keep me busy. Mapfact's Dynamic AI Creator is also a fun mission editor tool that allows for dynamic missions based on user defined combat zones.
EDIT: DMA has also released GRAA Modpack. Still mainly using DMA Army but play some single missions with GRAA. I also like the SLX Mod of which I mainly use the Grouplink 3 mod to improve the AI (I edit my configs to run it with the other mods). DXDLL is also nice to improve the look of OFP but it used to interfere with Xfire's ingame chat so I uninstalled it.