I answered old EV questions, but here it is in one place:
Palpitoad in Icirrus City (40%). 2 HP EVs.
Ducklett on Driftveil Drawbridge (100%). 1 HP EV
Route 1, which has Lillipups and Patrats (both gives 1 Attack EV). BEWARE OF SHAKING SPOTS (2 HP EVs Audinos)
Roggerola in Wellspring Cave. 50%. 1 Def EV. (the other 50% are Woobats, which give 1 Speed EV)
SPECIAL ATTACK spots
Celestial Tower. Both Litwicks and Elgyems give 1 Sp.Att EV. (lower floors are more likely to be Litwicks, while higher are more likely to be Elgyems)
SPECIAL DEFENSE spots
Frillish on Route 17. 100%. 1 SpDef EV. Surfing.
Woobat in Wellspring Cave. 50%. (the other 50% are Roggerolas, which give 1 Def EV)
Basculin on Route 1. 100% (beware of bubbles*). 2 EVs. Surfing
*Feebas also gives 1 Speed EV, but Milotic (5%) gives 2 Sp.Def EVs